我的WCF4 Rest Service及Entity Framework with POCO之旅(四)——定制Entity

本文将focus几个结合使用WCF REST和Entity Framework with POCO的常见问题。

Entity Type和Property名称的大小写

按照RESTful的习惯,XML或者JSON格式的数据的node名称开头字母一般使用小写,比如,下面是一段Google Buzz API的RESTful返回信息:

<entry xmlns="http://www.w3.org/2005/Atom" xmlns:activity="http://activitystrea.ms/spec/1.0">
  <id>tag:google.com,2010:buzz:z12puk22ajfyzsz</id>
  <author>
    <name>Ted Taco</name>
    <uri>http://www.google.com/profiles/ted</uri>
  </author>
  <published>2010-04-23T11:03:34.342Z</published>
  <updated>2010-04-23T11:03:34.342Z</updated>
  <activity:object>
    <activity:object-type>http://activitystrea.ms/schema/1.0/note</activity:object-type>
    <content type="html">Hey, this is my first Buzz Post!</content>
  <activity:object>
  <link rel="alternate" type="text/html" href="http://www.google.com/buzz/ted/Hey-this-is-my-first-Buzz-Post" />
  <!-- more data -->
</entry>

要让我们的Service返回数据node也使用小写字母开头,我们需要给Entity加上[DataContract]和[DataMember] attributes。(当然也可以修改WCF的behavior让它使用我们提供的的serializer但是现在框架既然还能满足需求,我还不想那么做。)
手动加attribute显然不是一个好主意,而且可以想见一旦模型代码重新生成,我们的修改就都没了。我们需要修改生成Entity的T4模板(Model.tt和Model.Context.tt)。
T4模板和其他的一些代码生成器的模板很相似,和现在的ASP.NET也有点相似。主要特点就是在模板内容(对于模板来说类似于纯文本)中嵌入C#代码。
由于T4模板的可读性不是很好,而VS原生又不支持T4的高亮和intellisense,开始编辑之前,最好装一个支持T4高亮的插件。我用的是Visual T4,虽然反应比较慢还有一些bug,不过是免费的,基本也够用了。

我们先看一下现在的Model.tt的全貌:

<#@ template language="C#" debug="false" hostspecific="true"#>
<#@ include file="EF.Utility.CS.ttinclude"#><#@
 output extension=".cs"#><#

CodeGenerationTools code = new CodeGenerationTools(this);
MetadataLoader loader = new MetadataLoader(this);
CodeRegion region = new CodeRegion(this, 1);
MetadataTools ef = new MetadataTools(this);

string inputFile = @"WcfRestServiceDemo.edmx";
EdmItemCollection ItemCollection = loader.CreateEdmItemCollection(inputFile);
string namespaceName = code.VsNamespaceSuggestion();

EntityFrameworkTemplateFileManager fileManager = EntityFrameworkTemplateFileManager.Create(this);

// Write out support code to primary template output file
WriteHeader(fileManager);
BeginNamespace(namespaceName, code);
WriteCustomObservableCollection();
EndNamespace(namespaceName);

// Emit Entity Types
foreach (EntityType entity in ItemCollection.GetItems<EntityType>().OrderBy(e => e.Name))
{
    fileManager.StartNewFile(entity.Name + ".cs");
    BeginNamespace(namespaceName, code);
    bool entityHasNullableFKs = entity.NavigationProperties.Any(np => np.GetDependentProperties().Any(p=>ef.IsNullable(p)));
#>
<#=Accessibility.ForType(entity)#> <#=code.SpaceAfter(code.AbstractOption(entity))#>partial class <#=code.Escape(entity)#><#=code.StringBefore(" : ", code.Escape(entity.BaseType))#>
{
<#
    region.Begin("Primitive Properties");

    foreach (EdmProperty edmProperty in entity.Properties.Where(p => p.TypeUsage.EdmType is PrimitiveType && p.DeclaringType == entity))
    {
        bool isForeignKey = entity.NavigationProperties.Any(np=>np.GetDependentProperties().Contains(edmProperty));
        bool isDefaultValueDefinedInModel = (edmProperty.DefaultValue != null);
        bool generateAutomaticProperty = false;

#>

    <#=PropertyVirtualModifier(Accessibility.ForProperty(edmProperty))#> <#=code.Escape(edmProperty.TypeUsage)#> <#=code.Escape(edmProperty)#>
    {
<#
        if (isForeignKey)
        {
#>
        <#=code.SpaceAfter(Accessibility.ForGetter(edmProperty))#>get { return <#=code.FieldName(edmProperty)#>; }
        <#=code.SpaceAfter(Accessibility.ForSetter(edmProperty))#>set
        {
<#
            if (entityHasNullableFKs)
            {
#>
            try
            {
                _settingFK = true;
<#
                PushIndent(CodeRegion.GetIndent(1));
            }
            if (((PrimitiveType)edmProperty.TypeUsage.EdmType).PrimitiveTypeKind == PrimitiveTypeKind.Binary)
            {
#>
            if (!StructuralComparisons.StructuralEqualityComparer.Equals(<#=code.FieldName(edmProperty)#>, value))
<#
            }
            else
            {
#>
            if (<#=code.FieldName(edmProperty)#> != value)
<#
            }
#>
            {
<#
            foreach (var np in entity.NavigationProperties.Where(np=>np.GetDependentProperties().Contains(edmProperty)))
            {
                EdmProperty principalProperty = ef.GetCorrespondingPrincipalProperty(np, edmProperty);
                if (((PrimitiveType)principalProperty.TypeUsage.EdmType).PrimitiveTypeKind == PrimitiveTypeKind.Binary)
                {
#>
                if ((<#=code.Escape(np)#> != null) && !StructuralComparisons.StructuralEqualityComparer.Equals(<#=code.Escape(np)#>.<#=code.Escape(principalProperty)#>, value))
<#
                }
                else
                {
#>
                if (<#=code.Escape(np)#> != null && <#=code.Escape(np)#>.<#=code.Escape(principalProperty)#> != value)
<#
                }
#>
                {
<#
                if (!(np.GetDependentProperties().Where(p=>ef.IsNullable(p)).Any() &&
                      np.GetDependentProperties().Count() > 1))
                {
#>
                    <#=code.Escape(np)#> = null;
<#
                }
                else
                {
#>
                    var previousValue = <#=code.FieldName(np)#>;
                    <#=code.FieldName(np)#> = null;
                    Fixup<#=np.Name#>(previousValue, skipKeys: true);
<#
                }
#>
                }
<#
            }
#>
                <#=code.FieldName(edmProperty)#> = value;
            }
<#
            if (entityHasNullableFKs)
            {
                PopIndent();
#>
            }
            finally
            {
                _settingFK = false;
            }
<#
            }
#>
        }
<#
        }
        else if (isDefaultValueDefinedInModel)
        {
#>
        <#=code.SpaceAfter(Accessibility.ForGetter(edmProperty))#>get { return <#=code.FieldName(edmProperty)#>; }
        <#=code.SpaceAfter(Accessibility.ForSetter(edmProperty))#>set { <#=code.FieldName(edmProperty)#> = value; }
<#
        }
        else
        {
            generateAutomaticProperty = true;
#>
        <#=code.SpaceAfter(Accessibility.ForGetter(edmProperty))#>get;
        <#=code.SpaceAfter(Accessibility.ForSetter(edmProperty))#>set;
<#
        }
#>
    }
<#
        if (!generateAutomaticProperty)
        {
#>
    private <#=code.Escape(edmProperty.TypeUsage)#> <#=code.FieldName(edmProperty)#><#=code.StringBefore(" = ", code.CreateLiteral(edmProperty.DefaultValue))#>;
<#
        }
    }
    region.End();

    region.Begin("Complex Properties");

    foreach(EdmProperty edmProperty in entity.Properties.Where(p => p.TypeUsage.EdmType is ComplexType && p.DeclaringType == entity))
    {
#>

    <#=PropertyVirtualModifier(Accessibility.ForProperty(edmProperty))#> <#=code.Escape(edmProperty.TypeUsage)#> <#=code.Escape(edmProperty)#>
    {
        <#=code.SpaceAfter(Accessibility.ForGetter(edmProperty))#>get { return <#=code.FieldName(edmProperty)#>; }
        <#=code.SpaceAfter(Accessibility.ForSetter(edmProperty))#>set { <#=code.FieldName(edmProperty)#> = value; }
    }
    private <#=code.Escape(edmProperty.TypeUsage)#> <#=code.FieldName(edmProperty)#> = new <#=code.Escape(edmProperty.TypeUsage)#>();
<#
    }

    region.End();

    ////////
    //////// Write Navigation properties -------------------------------------------------------------------------------------------
    ////////

    region.Begin("Navigation Properties");

    foreach (NavigationProperty navProperty in entity.NavigationProperties.Where(np => np.DeclaringType == entity))
    {
        NavigationProperty inverse = ef.Inverse(navProperty);
        if (inverse != null &&  !IsReadWriteAccessibleProperty(inverse))
        {
            inverse = null;
        }
#>

<#
        if (navProperty.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many)
        {
#>
    <#=PropertyVirtualModifier(Accessibility.ForReadOnlyProperty(navProperty))#> ICollection<<#=code.Escape(navProperty.ToEndMember.GetEntityType())#>> <#=code.Escape(navProperty)#>
    {
        get
        {
            if (<#=code.FieldName(navProperty)#> == null)
            {
<#
                if (inverse != null || ((AssociationType)navProperty.RelationshipType).IsForeignKey)
                {
#>
                var newCollection = new FixupCollection<<#=code.Escape(navProperty.ToEndMember.GetEntityType())#>>();
                newCollection.CollectionChanged += Fixup<#=navProperty.Name#>;
                <#=code.FieldName(navProperty)#> = newCollection;
<#
                }
                else
                {
#>
                <#=code.FieldName(navProperty)#> = new FixupCollection<<#=code.Escape(navProperty.ToEndMember.GetEntityType())#>>();
<#
                }
#>
            }
            return <#=code.FieldName(navProperty)#>;
        }
        set
        {
<#
            if (inverse != null || ((AssociationType)navProperty.RelationshipType).IsForeignKey)
            {
#>
            if (!ReferenceEquals(<#=code.FieldName(navProperty)#>, value))
            {
                var previousValue = <#=code.FieldName(navProperty)#> as FixupCollection<<#=code.Escape(navProperty.ToEndMember.GetEntityType())#>>;
                if (previousValue != null)
                {
                    previousValue.CollectionChanged -= Fixup<#=navProperty.Name#>;
                }
                <#=code.FieldName(navProperty)#> = value;
                var newValue = value as FixupCollection<<#=code.Escape(navProperty.ToEndMember.GetEntityType())#>>;
                if (newValue != null)
                {
                    newValue.CollectionChanged += Fixup<#=navProperty.Name#>;
                }
            }
<#
            }
            else
            {
#>
            <#=code.FieldName(navProperty)#> = value;
<#
            }
#>
        }
    }
    private ICollection<<#=code.Escape(navProperty.ToEndMember.GetEntityType())#>> <#=code.FieldName(navProperty)#>;
<#
        }
        else
        {
#>
    <#=PropertyVirtualModifier(Accessibility.ForProperty(navProperty))#> <#=code.Escape(navProperty.ToEndMember.GetEntityType())#> <#=code.Escape(navProperty)#>
    {
<#
            if (inverse != null || ((AssociationType)navProperty.RelationshipType).IsForeignKey)
            {
#>
        <#=code.SpaceAfter(Accessibility.ForGetter(navProperty))#>get { return <#=code.FieldName(navProperty)#>; }
        <#=code.SpaceAfter(Accessibility.ForSetter(navProperty))#>set
        {
            if (!ReferenceEquals(<#=code.FieldName(navProperty)#>, value))
            {
                var previousValue = <#=code.FieldName(navProperty)#>;
                <#=code.FieldName(navProperty)#> = value;
                Fixup<#=navProperty.Name#>(previousValue);
            }
        }
    }
    private <#=code.Escape(navProperty.ToEndMember.GetEntityType())#> <#=code.FieldName(navProperty)#>;
<#
            }
            else
            {
#>
        <#=code.SpaceAfter(Accessibility.ForGetter(navProperty))#>get;
        <#=code.SpaceAfter(Accessibility.ForSetter(navProperty))#>set;
    }
<#
            }
        }
    }
    region.End();

    region.Begin("Association Fixup");

    if (entityHasNullableFKs)
    {
#>

    private bool _settingFK = false;
<#
    }
    foreach (NavigationProperty navProperty in entity.NavigationProperties.Where(np => np.DeclaringType == entity))
    {
        NavigationProperty inverse = ef.Inverse(navProperty);

        if (inverse != null && !IsReadWriteAccessibleProperty(inverse))
        {
            inverse = null;
        }

        if ( (inverse != null || ((AssociationType)navProperty.RelationshipType).IsForeignKey) &&
             (navProperty.ToEndMember.RelationshipMultiplicity != RelationshipMultiplicity.Many) )
        {
            var skipKeysArgument = (navProperty.GetDependentProperties().Where(p=>ef.IsNullable(p)).Any() && navProperty.GetDependentProperties().Count() > 1)
                ? ", bool skipKeys = false"
                : String.Empty;
#>

    private void Fixup<#=navProperty.Name#>(<#=code.Escape(navProperty.ToEndMember.GetEntityType())#> previousValue<#= skipKeysArgument #>)
    {
<#
        if (inverse != null)
        {
            if (inverse.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many)
            {
#>
        if (previousValue != null && previousValue.<#=code.Escape(inverse)#>.Contains(this))
        {
            previousValue.<#=code.Escape(inverse)#>.Remove(this);
        }
<#
            }
            else
            {
#>
        if (previousValue != null && ReferenceEquals(previousValue.<#=code.Escape(inverse)#>, this))
        {
            previousValue.<#=code.Escape(inverse)#> = null;
        }
<#
            }

            if (inverse.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many)
            {
#>

        if (<#=code.Escape(navProperty)#> != null)
        {
            if (!<#=code.Escape(navProperty)#>.<#=code.Escape(inverse)#>.Contains(this))
            {
                <#=code.Escape(navProperty)#>.<#=code.Escape(inverse)#>.Add(this);
            }
<#
                foreach (var dependentProperty in navProperty.GetDependentProperties())
                {
                    EdmProperty principalProperty = ef.GetCorrespondingPrincipalProperty(navProperty, dependentProperty);
                    if (((PrimitiveType)principalProperty.TypeUsage.EdmType).PrimitiveTypeKind == PrimitiveTypeKind.Binary)
                    {
#>
            if (!StructuralComparisons.StructuralEqualityComparer.Equals(<#=code.Escape(dependentProperty)#>, <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>))
<#
                    }
                    else
                    {
#>
            if (<#=code.Escape(dependentProperty)#> != <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>)
<#
                    }
#>
            {
                <#=code.Escape(dependentProperty)#> = <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>;
            }
<#
                }
#>
        }
<#
                if (navProperty.GetDependentProperties().Where(p=>ef.IsNullable(p)).Any())
                {
                    if (navProperty.GetDependentProperties().Count() > 1)
                    {
#>
        else if (!_settingFK && !skipKeys)
<#
                    }
                    else
                    {
#>
        else if (!_settingFK)
<#
                    }
#>
        {
<#
                    foreach (var dependentProperty in navProperty.GetDependentProperties().Where(p => ef.IsNullable(p)))
                    {
#>
            <#=code.Escape(dependentProperty)#> = null;
<#
                    }
#>
        }
<#
                }
            }
            else
            {
#>

        if (<#=code.Escape(navProperty)#> != null)
        {
            <#=code.Escape(navProperty)#>.<#=code.Escape(inverse)#> = this;
<#
                foreach (var dependentProperty in navProperty.GetDependentProperties())
                {
                    EdmProperty principalProperty = ef.GetCorrespondingPrincipalProperty(navProperty, dependentProperty);
                    if (((PrimitiveType)principalProperty.TypeUsage.EdmType).PrimitiveTypeKind == PrimitiveTypeKind.Binary)
                    {
#>
            if (!StructuralComparisons.StructuralEqualityComparer.Equals(<#=code.Escape(dependentProperty)#>, <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>))
<#
                    }
                    else
                    {
#>
            if (<#=code.Escape(dependentProperty)#> != <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>)
<#
                    }
#>
            {
                <#=code.Escape(dependentProperty)#> = <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>;
            }
<#
                }
#>
        }
<#
            }
        }
        else
        {
            if (navProperty.GetDependentProperties().Any())
            {
#>
        if (<#=code.Escape(navProperty)#> != null)
        {
<#
                foreach (var dependentProperty in navProperty.GetDependentProperties())
                {
                    EdmProperty principalProperty = ef.GetCorrespondingPrincipalProperty(navProperty, dependentProperty);
                    if (((PrimitiveType)principalProperty.TypeUsage.EdmType).PrimitiveTypeKind == PrimitiveTypeKind.Binary)
                    {
#>
            if (!StructuralComparisons.StructuralEqualityComparer.Equals(<#=code.Escape(dependentProperty)#>, <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>))
<#
                    }
                    else
                    {
#>
            if (<#=code.Escape(dependentProperty)#> != <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>)
<#
                    }
#>
            {
                <#=code.Escape(dependentProperty)#> = <#=code.Escape(navProperty)#>.<#=code.Escape(principalProperty)#>;
            }
<#
                }
#>
        }
<#
                if (navProperty.GetDependentProperties().Where(p => ef.IsNullable(p)).Any())
                {
                    if (navProperty.GetDependentProperties().Count() > 1)
                    {
#>
        else if (!_settingFK && !skipKeys)
<#
                    }
                    else
                    {
#>
        else if (!_settingFK)
<#
                    }
#>
        {
<#
                    foreach (var dependentProperty in navProperty.GetDependentProperties().Where(p => ef.IsNullable(p)))
                    {
#>
            <#=code.Escape(dependentProperty)#> = null;
<#
                    }
#>
        }
<#
                }
            }
            else if (((AssociationType)navProperty.RelationshipType).IsForeignKey)
            {
#>
        if (<#=code.Escape(navProperty)#> != null)
        {
<#
                foreach (var fromProperty in ef.GetPrincipalProperties(navProperty))
                {
#>
            <#=code.Escape(navProperty)#>.<#=code.Escape(ef.GetCorrespondingDependentProperty(navProperty, fromProperty))#> = <#=code.Escape(fromProperty)#>;
<#
                }
#>
        }
<#
            }
        }
#>
    }
<#
        }
    }

    foreach (NavigationProperty navProperty in entity.NavigationProperties.Where(np => np.DeclaringType == entity))
    {
        NavigationProperty inverse = ef.Inverse(navProperty);

        if (inverse != null && !IsReadWriteAccessibleProperty(inverse))
        {
            inverse = null;
        }

        if ( (inverse != null || ((AssociationType)navProperty.RelationshipType).IsForeignKey) &&
             (navProperty.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many) )
        {
#>

    private void Fixup<#=navProperty.Name#>(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems != null)
        {
            foreach (<#=code.Escape(navProperty.ToEndMember.GetEntityType())#> item in e.NewItems)
            {
<#
                if (inverse != null)
                {
                    if (inverse.ToEndMember.RelationshipMultiplicity != RelationshipMultiplicity.Many)
                    {
#>
                item.<#=code.Escape(inverse)#> = this;
<#
                    }
                    else
                    {
#>
                if (!item.<#=code.Escape(inverse)#>.Contains(this))
                {
                    item.<#=code.Escape(inverse)#>.Add(this);
                }
<#
                    }
                }
                else if (((AssociationType)navProperty.RelationshipType).IsForeignKey)
                {
                    foreach (var fromProperty in ef.GetPrincipalProperties(navProperty))
                    {
#>
                item.<#=code.Escape(ef.GetCorrespondingDependentProperty(navProperty, fromProperty))#> = <#=code.Escape(fromProperty)#>;
<#
                    }
                }
#>
            }
        }

        if (e.OldItems != null)
        {
            foreach (<#=code.Escape(navProperty.ToEndMember.GetEntityType())#> item in e.OldItems)
            {
<#
                if (inverse != null)
                {
                    if (inverse.ToEndMember.RelationshipMultiplicity != RelationshipMultiplicity.Many)
                    {
#>
                if (ReferenceEquals(item.<#=code.Escape(inverse)#>, this))
                {
                    item.<#=code.Escape(inverse)#> = null;
                }
<#
                    }
                    else
                    {
#>
                if (item.<#=code.Escape(inverse)#>.Contains(this))
                {
                    item.<#=code.Escape(inverse)#>.Remove(this);
                }
<#
                    }
                }
                else if (((AssociationType)navProperty.RelationshipType).IsForeignKey)
                {
                    foreach (var fromProperty in ef.GetPrincipalProperties(navProperty))
                    {
                        var p = ef.GetCorrespondingDependentProperty(navProperty, fromProperty);
                        if (ef.IsNullable(p.TypeUsage))
                        {
#>
                item.<#=code.Escape(p)#> = null;
<#
                        }
                    }
                }
;#>
            }
        }
    }
<#
        }
    }

    region.End();
#>
}
<#
    EndNamespace(namespaceName);
}

foreach (ComplexType complex in ItemCollection.GetItems<ComplexType>().OrderBy(e => e.Name))
{
    fileManager.StartNewFile(complex.Name + ".cs");
    BeginNamespace(namespaceName, code);
#>
<#=Accessibility.ForType(complex)#> partial class <#=code.Escape(complex)#>
{
<#
    region.Begin("Primitive Properties");

    foreach(EdmProperty edmProperty in complex.Properties.Where(p => p.TypeUsage.EdmType is PrimitiveType && p.DeclaringType == complex))
    {
        bool isDefaultValueDefinedInModel = (edmProperty.DefaultValue != null);
#>

    <#=Accessibility.ForProperty(edmProperty)#> <#=code.Escape(edmProperty.TypeUsage)#> <#=code.Escape(edmProperty)#>
<#
        if (isDefaultValueDefinedInModel)
        {
#>
    {
        <#=code.SpaceAfter(Accessibility.ForGetter(edmProperty))#>get { return <#=code.FieldName(edmProperty)#>; }
        <#=code.SpaceAfter(Accessibility.ForSetter(edmProperty))#>set { <#=code.FieldName(edmProperty)#> = value; }
    }
    private <#=code.Escape(edmProperty.TypeUsage)#> <#=code.FieldName(edmProperty)#><#=code.StringBefore(" = ", code.CreateLiteral(edmProperty.DefaultValue))#>;
<#
        }
        else
        {
#>
    {
        <#=code.SpaceAfter(Accessibility.ForGetter(edmProperty))#>get;
        <#=code.SpaceAfter(Accessibility.ForSetter(edmProperty))#>set;
    }
<#
        }
    }

    region.End();

    region.Begin("Complex Properties");

    foreach(EdmProperty edmProperty in complex.Properties.Where(p => p.TypeUsage.EdmType is ComplexType && p.DeclaringType == complex))
    {
#>

    <#=Accessibility.ForProperty(edmProperty)#> <#=code.Escape(edmProperty.TypeUsage)#> <#=code.Escape(edmProperty)#>
    {
        <#=code.SpaceAfter(Accessibility.ForGetter(edmProperty))#>get { return <#=code.FieldName(edmProperty)#>; }
        <#=code.SpaceAfter(Accessibility.ForSetter(edmProperty))#>set { <#=code.FieldName(edmProperty)#> = value; }
    }
    private <#=code.Escape(edmProperty.TypeUsage)#> <#=code.FieldName(edmProperty)#> = new <#=code.Escape(edmProperty.TypeUsage)#>();
<#
    }

    region.End();
#>
}
<#
    EndNamespace(namespaceName);
}

if (!VerifyTypesAreCaseInsensitiveUnique(ItemCollection))
{
    return "";
}

fileManager.Process();

#>
<#+
void WriteHeader(EntityFrameworkTemplateFileManager fileManager, params string[] extraUsings)
{
    fileManager.StartHeader();
#>
//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated from a template.
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
<#=String.Join(String.Empty, extraUsings.Select(u => "using " + u + ";" + Environment.NewLine).ToArray())#>
<#+
    fileManager.EndBlock();
}

void BeginNamespace(string namespaceName, CodeGenerationTools code)
{
    CodeRegion region = new CodeRegion(this);
    if (!String.IsNullOrEmpty(namespaceName))
    {
#>
namespace <#=code.EscapeNamespace(namespaceName)#>
{
<#+
        PushIndent(CodeRegion.GetIndent(1));
    }
}


void EndNamespace(string namespaceName)
{
    if (!String.IsNullOrEmpty(namespaceName))
    {
        PopIndent();
#>
}
<#+
    }
}

bool IsReadWriteAccessibleProperty(EdmMember member)
{
    string setter = Accessibility.ForWriteOnlyProperty(member);
    string getter = Accessibility.ForReadOnlyProperty(member);

    return getter != "private" && getter != "protected" && setter != "private" && setter != "protected";
}

string PropertyVirtualModifier(string accessibility)
{
    return accessibility + (accessibility != "private" ? " virtual" : "");
}

void WriteCustomObservableCollection()
{
#>
// An System.Collections.ObjectModel.ObservableCollection that raises
// individual item removal notifications on clear and prevents adding duplicates.
public class FixupCollection<T> : ObservableCollection<T>
{
    protected override void ClearItems()
    {
        new List<T>(this).ForEach(t => Remove(t));
    }

    protected override void InsertItem(int index, T item)
    {
        if (!this.Contains(item))
        {
            base.InsertItem(index, item);
        }
    }
}
<#+
}

bool VerifyTypesAreCaseInsensitiveUnique(EdmItemCollection itemCollection)
{
    Dictionary<string, bool> alreadySeen = new Dictionary<string, bool>(StringComparer.OrdinalIgnoreCase);
    foreach(StructuralType type in itemCollection.GetItems<StructuralType>())
    {
        if (!(type is EntityType || type is ComplexType))
        {
            continue;
        }

        if (alreadySeen.ContainsKey(type.FullName))
        {
            Error(String.Format(CultureInfo.CurrentCulture, "This template does not support types that differ only by case, the types {0} are not supported", type.FullName));
            return false;
        }
        else
        {
            alreadySeen.Add(type.FullName, true);
        }

    }

    return true;
}
#>

看起来很长?其实主要内容并不复杂。我们所要关心的的Entity生成代码都在一个遍历所有entity的foreach中,对于每个entity,它依次枚举Primitive Properties - entity本身定义的基本类型字段,Complex Properties - 用户定义的复杂类型字段,以及Navigation Properties - entity的关系字段。

首先找到生成每个类定义的代码:

<#=Accessibility.ForType(entity)#> <#=code.SpaceAfter(code.AbstractOption(entity))#>partial class <#=code.Escape(entity)#><#=code.StringBefore(" : ", code.Escape(entity.BaseType))#>

在上面加一行:

[DataContract(Name = "<#=char.ToLowerInvariant(entity.Name[0]) + entity.Name.Substring(1) #>")]

然后再找到生成Primitive Property的代码(其他的类似):

<#=PropertyVirtualModifier(Accessibility.ForProperty(edmProperty))#> <#=code.Escape(edmProperty.TypeUsage)#> <#=code.Escape(edmProperty)#>

在上面加一行:

[DataMember(Name = "<#=char.ToLowerInvariant(edmProperty.Name[0]) + edmProperty.Name.Substring(1) #>")]

由于DataContract在System.Runtime.Serialization命名空间下,我们还需要添加命名空间。在接近Model.tt末尾的地方找到有一堆命名空间定义,在末尾加上:

using System.Runtime.Serialization;

然后Save,这时代码会重新生成,我们再看一下这时的Microblog.cs:

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated from a template.
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Runtime.Serialization;

namespace WcfRestServiceDemo.Data
{
    [DataContract(Name = "microblog")]
    public partial class Microblog
    {
        #region Primitive Properties
        [DataMember(Name = "id")]
        public virtual int Id
        {
            get;
            set;
        }
        [DataMember(Name = "content")]
        public virtual string Content
        {
            get;
            set;
        }
        [DataMember(Name = "publishTime")]
        public virtual System.DateTime PublishTime
        {
            get;
            set;
        }

        #endregion
    }
}

这时如果测试一下服务,就可以看到不论是XML还是JSON的返回结果中的字段都已经变成小写字母开头了。

需要注意的是,不仅是返回,这时客户端发送请求时,对应字段也必须同样改成小写字母开头。


处理Null值属性

为了引入这个问题,我们将服务稍稍变得复杂一些。假设现在并且每条微博可以关联一张图片,用户只要在写微博同时,输入图片地址即可。那么修改Microblog模型,添加Picture属性,包含一个图片的URL。由于图片是可选的,所以还要将的Nullable设为true。

如下:

imageimage

由于修改了EntityModel,需要在两个.tt模板文件上右键选择Run Custom Tools来生成新的POCO entity.

然后我们看一下服务的返回:

<ArrayOfmicroblog xmlns="http://schemas.datacontract.org/2004/07/WcfRestServiceDemo.Data" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
  <microblog>
    <content>Microblog with no picture.</content>
    <id>1</id>
    <picture i:nil="true"/>
    <publishTime>2011-04-19T22:00:00</publishTime>
  </microblog>
  <microblog>
    <content>Microblog with picture</content>
    <id>2</id>
    <picture>http://somepicture/somepicture</picture>
    <publishTime>2011-04-19T22:00:00</publishTime>
  </microblog>
</ArrayOfmicroblog>

这里有两条microblog,一条有picture,一条没有。但是没有picture的那个也把picture字段给返回了,只是用i:nil=”true”来标识这是个null值。显然这不是理想方式,想象一下一个entity可能会有很多可空的属性,尤其是当一个entity与许多其他entity产生关联,引入了许多navigation properties时,传输这些空属性将严重影响可读性(虽然大多数情况下应该不是人来读)并对性能造成影响(传输、序列化和反序列化)。(当然这不是绝对的,nil值有其应用场景,请根据实际情况决定

幸好DataMember attribute还有一个EmitDefaultValue属性,可以指定是否要序列化默认值。用和刚才类似的方法,修改T4模板,修改Property定义上方的[DataMember]:

    [DataMember(Name = "<#=char.ToLowerInvariant(edmProperty.Name[0]) + edmProperty.Name.Substring(1) #>"<#
if(edmProperty.Nullable)
{
	#>, EmitDefaultValue = false<#
}
#>)]
首先判断了property是否可设为null,若可以才省略空值。否则对于一个int属性,值为0时它就不会被传输了,这一般是不太合适的。(确切的讲,这里的Nullable和数据类型没有关系,指的是在数据模型中的nullable,也就是是否为可空字段。)

再次访问服务:

<ArrayOfmicroblog xmlns="http://schemas.datacontract.org/2004/07/WcfRestServiceDemo.Data" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
  <microblog>
    <content>Microblog with no picture.</content>
    <id>1</id>
    <publishTime>2011-04-19T22:00:00</publishTime>
  </microblog>
  <microblog>
    <content>Microblog with picture</content>
    <id>2</id>
    <picture>http://somepicture/somepicture</picture>
    <publishTime>2011-04-19T22:00:00</publishTime>
  </microblog>
</ArrayOfmicroblog>

可以看到没有图片的那个microblog的picture属性已经被省略了。


JSON中的DateTime

在第二章末尾我们提到过DateTime属性在JSON表示下的奇怪格式。严格来说,这不算什么问题,因为既然微软选择了这种格式,那么全世界的人都在碰到这个问题,相应的客户端解决方案也有很多。比如:

如果一定要从服务端解决这个问题的话,最根本的方法是改用自定义的序列化器。而比较简单的方法是为entity写一个partial类,然后提供一个long格式的对应属性:

using System;
using System.Runtime.Serialization;

namespace WcfRestServiceDemo.Data
{
    partial class Microblog
    {
        private static readonly DateTime _baseTime =
            new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).ToLocalTime();

        [DataMember(Name = "publishTimeSec")]
        public long PublishTimeSeconds
        {
            get { return (long)(PublishTime - _baseTime).TotalMilliseconds; }
            set { PublishTime = _baseTime.AddMilliseconds(value); }
        }
    }
}

这时服务的返回就是:

[
 {
  "content":"Microblog with no picture.",
  "id":1,
  "publishTime":"\/Date(1303221600000+0800)\/",
  "publishTimeSec":1303221600000
 },
 {
  "content":"Microblog with picture",
  "id":2,
  "picture":"http:\/\/somepicture\/somepicture",
  "publishTime":"\/Date(1303221600000+0800)\/",
  "publishTimeSec":1303221600000
 }
]

当然更绝的做法是把这个替代属性的生成也交给T4模板来做。具体做法请参考我整理好后上传的代码


小结

本文介绍了:

  • 如何修改T4模板控制模型代码的生成,包括修改Type名称、属性名称的起始字母大小写和是否要序列化默认值的选项
  • 如何用替代属性解决JSON中DateTime格式的问题。

我的WCF4 REST Service及Entity Framework with POCO之旅系列

posted on 2011-04-20 10:44  Gildor Wang  阅读(2753)  评论(6编辑  收藏  举报

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