匿名类型 使用泛型T linq返回dynamic类型的匿名实体 如何把匿名类型.GetType()返回的对象传进泛型里面 EF实体查询出的数据List<T>转DataTable出现【DataSet 不支持 System.Nullable<>】的问题

[100分]紧急求助：LinQ下使用IQueryable<T>如何将返回类型<T>使用匿名类型

问题描述如下：
我有一个方法如下：
public IQueryable DissensionList(Guid guid)
    {
        var p = from d in db.T_民事调解 where (d.社区Guid == guid) select new {序号=d.ID,d.纠纷甲方,d.纠纷乙方,d.调解人,d.调解时间,d.纠纷类别 };
        return p;
    }
现因为需求改变，需要在返回的IQueryable中使用Linq进行再次查询、筛选，但现在返回的类别为IQueryable，而IQueryable不能使用LinQ查询，
但是IQueryable<T>可以，但是<T>的类型是由方法内部中的
select new {序号=d.ID,d.纠纷甲方,d.纠纷乙方,d.调解人,d.调解时间,d.纠纷类别 };
来确定的，而且这个类型是不确定的，现疑问如下：
如何将这个返回的<T>类型设为匿名类型，由返回类型来自适应生成。
或者提供其它解决方案，返回方法内部生成的匿名类型相对应的List<T>或IQueryable<T>谢谢！

 

看了你的帖子，经过3天的努力我帮你总结了两个可行的方案，第一个方案比较简单点。第二个比较难

  方案一：   利用自建类型
  
  public IEnumerable<dd> get()
        {
            IEnumerable<dd> re = from n in gj.zuixinZhaosheng
                                 select new dd { id = n.id, jz = n.jianzhang };
            return re;

        }
        
        
        //手动创建对象类型
        public class dd
        {
            public int id { get; set; }
            public string jz { get; set; }

        }
        
        
        
        
        客户代码、
        
           protected void Button1_Click(object sender, EventArgs e)
        {
            zuixinZhaoshengbll b = zuixinZhaoshengbll.getinstance();


            foreach (var item in b.get())
            {

                Response.Write(item.id.ToString() + "</br>");
                Response.Write(item.jz.ToString() + "</br>");
            }


        }
        
        
        方案二： 反射方法
        
        
        using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Reflection;
namespace AnonymouseType
{
    class AnonymouseSolve
    {
        //取得ProductID,ProductName，CategoryName
        public IEnumerable GetAnonymousResult()
        {
            NorthwindDataContext db = new NorthwindDataContext();
            var result = db.Products.Select(p => new
            {
                产品ID = p.ProductID,
                产品名称 = p.ProductName,
                类别名称 = p.Category.CategoryName
            });
            return result;
        }
        //取得ProductID,ProductName，CategoryName的前10条记录
        public IEnumerable GetTop10Result(IEnumerable _result)
        {
            var result = _result.Cast<object>();
            var set = result.Select(p => new
            {   //利用反射取得传入的匿名类型的信息
                产品ID = p.GetType().GetProperty("产品ID").GetValue(p, null).ToString(),
                产品名称 = p.GetType().GetProperty("产品名称").GetValue(p, null).ToString(),
                类别名称 = p.GetType().GetProperty("类别名称").GetValue(p, null).ToString()
            }).Take(10);
            return set;
        }
        public IEnumerable GetTop10Result(object IEnumerableOject)
        {
            var result = (IEnumerable)IEnumerableOject;
            return this.GetTop10Result(result);
        }
    }
}




测试
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Reflection;
namespace AnonymouseType
{
    class Program
    {
        static void Main(string[] args)
        {
            AnonymouseSolve solve = new AnonymouseSolve();

            foreach (var item in solve.GetTop10Result(solve.GetAnonymousResult()))
            {
                Console.WriteLine("-----------------------------------------");
                Type itemType = item.GetType();
                Console.WriteLine("产品ID:" + itemType.GetProperty("产品ID").GetValue(item, null));
                Console.WriteLine("产品名称:" + itemType.GetProperty("产品名称").GetValue(item, null));
                Console.WriteLine("类别名称:" + itemType.GetProperty("类别名称").GetValue(item, null));
                Console.WriteLine("-----------------------------------------");
                Console.WriteLine();
            }


            var obj = (object)solve.GetAnonymousResult();
            foreach (var item in solve.GetTop10Result(obj))
            {
                Console.WriteLine("-----------------------------------------");
                Type itemType = item.GetType();
                Console.WriteLine("产品ID:" + itemType.GetProperty("产品ID").GetValue(item, null));
                Console.WriteLine("产品名称:" + itemType.GetProperty("产品名称").GetValue(item, null));
                Console.WriteLine("类别名称:" + itemType.GetProperty("类别名称").GetValue(item, null));
                Console.WriteLine("-----------------------------------------");
                Console.WriteLine();
            }

        }
    }
}

 

 

 

linq返回dynamic类型的匿名实体

 

这样会报错：

复制代码
void Main()
{
    var  x=GetSpareInfoByCode();
    Console.Write(x.Key);//报错：“object”未包含“Key”的定义
}
    public dynamic  GetSpareInfoByCode(){
    var words =
        from word in "The quick brown fox jumps over the lazy dog".Split()
        orderby word.ToUpper()
        select word;
        
    var duplicates =
        from word in words
        group word.ToUpper() by word.ToUpper() into g
        where g.Count() > 1
        select new { g.Key, Count = g.Count() };
            return duplicates;
        }
复制代码

 

使用tolist

复制代码
void Main()
{
    //var  x=GetSpareInfoByCode();
    IEnumerable<object> y=GetSpareInfoByCode();
    //foreach (var item in (IEnumerable<object>)x)
    foreach (var item in y)
    {
        Console.Write(item.GetType().GetProperty("Key").GetValue(item, null));
        Console.Write(item.GetType().GetProperty("Count").GetValue(item, null));
    }
}
    public dynamic  GetSpareInfoByCode(){
    var words =
        from word in "The quick brown fox jumps over the lazy dog".Split()
        orderby word.ToUpper()
        select word;
        
    var duplicates =
        from word in words
        group word.ToUpper() by word.ToUpper() into g
        where g.Count() > 1
        select new { g.Key, Count = g.Count() };
            return duplicates.ToList();
        }
复制代码

有木有更简单高效的方式呢

 

 

 

如何把匿名类型.GetType()返回的对象传进泛型里面

 
复制代码
//怎么取得匿名类型的Type放到
//泛型T当中？？

var 匿名 = new {
 A = 0,
 B = 1 };
Type t = 匿名.GetType();

//然后下面
var xx = dbContext.Database.SqlQuery<t>("sql");
//就悲剧了

var xx2 = dbContext.Database.SqlQuery<dynamic>("sql");
//xx2有列表,但是都是Object..~~~无法显示真实项,用Profile跟..SQL确实提交了.
求解释
复制代码

msdn大神的解决办法

看到了所以记录下来

出现那个问题的原因是动态类型上没有 Entity Framework 需要的属性定义，Entity Framework 是通过反射类型上的属性来做映射的。为了解决这个问题，我用到了 Emit 技术，动态产生一个类型，并且动态写入 IL 代码产生属性。

代码如下，测试在 C# 4.0 上通过。
复制代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Entity;
using System.Collections;
using System.Reflection.Emit;
using System.Reflection;
 
namespace Demo
{
  public class Program
  {
    public static void Main(string[] args)
    {
      string connectionString = "Server=(local); Integrated Security=true; Database=master";
      using (DbContext context = new DbContext(connectionString))
      {
        TypeBuilder builder = Program.CreateTypeBuilder("MyDynamicAssembly", "MyModule", "MyType");
        Program.CreateAutoImplementedProperty(builder, "name", typeof(string));
        Program.CreateAutoImplementedProperty(builder, "type", typeof(string));
        Program.CreateAutoImplementedProperty(builder, "id", typeof(int));
 
        Type resultType = builder.CreateType();
 
        dynamic queryResult = context.Database.SqlQuery(resultType, "SELECT * FROM sys.sysobjects");
 
        Console.WriteLine("{0,20} {1,4} {2,10}", "Name", "Type", "ID");
        foreach (dynamic item in queryResult)
        {
          Console.WriteLine("{0,10} {1,4} {2,10}", item.name, item.type, item.id);
        }
      }
 
      Console.ReadKey();
    }
 
    public static TypeBuilder CreateTypeBuilder(string assemblyName, string moduleName, string typeName)
    {
      TypeBuilder typeBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName(assemblyName), AssemblyBuilderAccess.Run).DefineDynamicModule(moduleName).DefineType(typeName, TypeAttributes.Public);
      typeBuilder.DefineDefaultConstructor(MethodAttributes.Public);
      return typeBuilder;
    }
 
    public static void CreateAutoImplementedProperty(TypeBuilder builder, string propertyName, Type propertyType)
    {
      const string PrivateFieldPrefix = "m_";
      const string GetterPrefix = "get_";
      const string SetterPrefix = "set_";
 
      // Generate the field.
      FieldBuilder fieldBuilder = builder.DefineField(string.Concat(PrivateFieldPrefix, propertyName), propertyType, FieldAttributes.Private);
 
      // Generate the property
      PropertyBuilder propertyBuilder = builder.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, null);
 
      // Property getter and setter attributes.
      MethodAttributes propertyMethodAttributes = MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig;
 
      // Define the getter method.
      MethodBuilder getterMethod = builder.DefineMethod(string.Concat(GetterPrefix, propertyName), propertyMethodAttributes, propertyType, Type.EmptyTypes);
 
      // Emit the IL code.
      // ldarg.0
      // ldfld,_field
      // ret
      ILGenerator getterILCode = getterMethod.GetILGenerator();
      getterILCode.Emit(OpCodes.Ldarg_0);
      getterILCode.Emit(OpCodes.Ldfld, fieldBuilder);
      getterILCode.Emit(OpCodes.Ret);
 
      // Define the setter method.
      MethodBuilder setterMethod = builder.DefineMethod(string.Concat(SetterPrefix, propertyName), propertyMethodAttributes, null, new Type[] { propertyType });
 
      // Emit the IL code.
      // ldarg.0
      // ldarg.1
      // stfld,_field
      // ret
      ILGenerator setterILCode = setterMethod.GetILGenerator();
      setterILCode.Emit(OpCodes.Ldarg_0);
      setterILCode.Emit(OpCodes.Ldarg_1);
      setterILCode.Emit(OpCodes.Stfld, fieldBuilder);
      setterILCode.Emit(OpCodes.Ret);
 
      propertyBuilder.SetGetMethod(getterMethod);
      propertyBuilder.SetSetMethod(setterMethod);
    }
  }
}
复制代码
 
 
 
 
 
 
 
 
 
 

EF实体查询出的数据List<T>转DataTable出现【DataSet 不支持 System.Nullable<>】的问题

 
复制代码
　　　　 public static DataTable ToDataTable<T>(this IEnumerable<T> varlist, CreateRowDelegate<T> fn)
        {
            DataTable dtReturn = new DataTable();
            // column names
            PropertyInfo[] oProps = null;
            // Could add a check to verify that there is an element 0
            foreach (T rec in varlist)
            {
                // Use reflection to get property names, to create table, Only first time, others will follow
                if (oProps == null)
                {
                    oProps = ((Type)rec.GetType()).GetProperties();
                    foreach (PropertyInfo pi in oProps)
                    {
                        Type colType = pi.PropertyType; if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition() == typeof(Nullable<>)))
                        {
                            colType = colType.GetGenericArguments()[0];
                        }
                        dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
                    }
                }
                DataRow dr = dtReturn.NewRow(); foreach (PropertyInfo pi in oProps)
                {
                    dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue(rec, null);
                }
                dtReturn.Rows.Add(dr);
            }
            return (dtReturn);
        }
        public delegate object[] CreateRowDelegate<T>(T t);
复制代码
List<T> list = DAL.ToList();
dataGridView1.DataSource = list.ToDataTable(a => new object[] { list });

以上代码可解决

posted @ 2018-10-26 10:57  ~雨落忧伤~  阅读(348)  评论(0)    收藏  举报