智能表单设计器Web Free Form Designer：FreeForm动态数据验证和动态自动计算

Posted on 2011-06-25 17:37 智能在线表单设计器 Web Form Builder 阅读(3853) 评论(7) 编辑收藏举报

FreeForm自动计算及数据验证

Silverlight中动态数据验证和动态自动计算的Reflection反射实现

上周在博客园发了个首页随笔，因为被误认为是广告而被移出首页，这次发首页，特地备足了技术材料，结合FreeForm实际的开发情况，从技术上分析在Silverlight中实现动态数据验证和自动计算的方法。我们知道在.Net 4.0标准类库中，反射的类很全，非常好用，但在Silverlight类库中涉及反射的命名空间虽然也有System.Reflection 和System.Reflection.Emit ，但类和方法大大的缩减了。以前我们在WinForm或者ASP.Net中实现动态验证和动态计算非常容易，可以通过类似如下代码实现：

View Code

// compile string code to create class, generate an intance and mothod

        public Expression(string expression, string fieldID, AppCom appcom)

        {

            this.Com = appcom;

            if (expression.IndexOf("return") < 0) expression = "return " + expression + ";";

            string className = "ExpressionValidate";

            string methodName = "Compute";

            if (!string.IsNullOrEmpty(fieldID))

            {

                methodName = ("Validate_" + fieldID).Replace(":", "_");

                methodName = methodName.Replace("@", "Att_");

            }

            CompilerParameters cp = new CompilerParameters();

            cp.GenerateInMemory = true;

            cp.ReferencedAssemblies.Add("System.dll");

            cp.ReferencedAssemblies.Add("mscorlib.dll");

            cp.ReferencedAssemblies.Add("System.Data.dll");

            cp.ReferencedAssemblies.Add("System.Xml.dll");

            // cp.ReferencedAssemblies.Add(Com.ClassDir + "ComFun_cs.dll");

            CompilerResults cr = new CSharpCodeProvider()

                .CompileAssemblyFromSource(cp, string.

              Format(@"using System;

                       using System.Text.RegularExpressions;

                       using System.Collections.Generic;

                       using System.Data.SqlClient;

                       using System.Xml;

                      sealed class {0}{{

                         XmlDocument xdoc;

                         XmlNamespaceManager nsmgr;

                         public bool {1}(){{

                            {2}

                         }}

                         {3}

                      }}",

              className, methodName, expression, appcom.ValidateComFuns) + Com.GetComFunInfo());

          

            instance = cr.CompiledAssembly.CreateInstance(className);

            method = instance.GetType().GetMethod(methodName);

 

            {

                MethodInfo SFun = instance.GetType().GetMethod("Initial");

                if (SFun != null)

                {

                    SFun.Invoke(instance, new object[] { AppCom.XDoc, AppCom.nsmgr });

                }

            }

            CLog.Win_ClassExp.AppendText(appcom.ValidateComFuns);

        }

 

        // validate one validation method

        public bool Compute()

        {

            return (bool)method.Invoke(instance, null);

        }

其中

sealed class {0}{{

XmlDocument xdoc;

XmlNamespaceManager nsmgr;

public bool {1}(){{

{2}

}}

{3}

}}

就是我们运行时从XML动态生成的类，从XML动态传入的参数，返回一个True 或 False的验证结果。参数分别对应如下：

{0}：className 类名

{1}：methodName 方法名

{2}：expression 动态验证表达式

{3}：动态加入的调用代码

很遗憾，这是在标准类库的快捷方便的写法，但是到了Silverlight微缩类库这里，很多类已不存在了。CodeDomProvider类没有了，Microsoft.VisualBasic

命名空间没有了，CompilerParameters 类没有了，CompilerResults类没有了，Microsoft.CSharp.CSharpCodeProvider类没有了，Microsoft.CSharp

下还有2个类：Microsoft.CSharp.RuntimeBinder. RuntimeBinderException类和Microsoft.CSharp.RuntimeBinder.RuntimeBinderInternalCompilerException，很明显这2个类是处理异常的。真的要绝望了。

经过捣腾System.Reflection.Assembly类，我们发现有4个方法：

System.Reflection.Assembly.GetCallingAssembly();

System.Reflection.Assembly.GetExecutingAssembly();

System.Reflection.Assembly.Load(assemblyName);

System.Reflection.Assembly.LoadFrom(assemblyFile);

发现Silverlight中的反射与.NET FRAMEWORK中的略有不同。以下分三种情况描述：

1：动态创建当前执行的程序集中的类实例。

2：动态创建XAP包中其它SILVERLIGHT程序集中的类实例。

3：动态下载并创建网站上其它SILVERLIGHT程序集中的类实例。

我们可以利用后两种方法来动态加载程序集，CSharpCodeProvider那种方便快捷的写法不可能用了，于是只能用System.Reflection.Emit 命名空间，定义动态程序集，关于这方面，微软有详细介绍：

http://msdn.microsoft.com/zh-cn/library/4xtysk39%28v=VS.95%29.aspx

首先需要了解生成方法体的 MSIL 指令代码，感觉和大学学的汇编差不多，

http://msdn.microsoft.com/zh-cn/library/system.reflection.emit.opcodes%28v=VS.95%29.aspx

贴一个通过Emit动态生成程序集的例子。其实是动态生成了这个类：

public class MyDynamicType

{

private int m_number;

public MyDynamicType() : this(42) {}

public MyDynamicType(int initNumber)

{

m_number = initNumber;

}

public int Number

{

get { return m_number; }

set { m_number = value; }

}

public int MyMethod(int multiplier)

{

return m_number * multiplier;

}

View Code

class Example

    {

        public static void Demo(System.Windows.Controls.TextBlock outputBlock)

        {

 

            AssemblyName aName = new AssemblyName("DynamicAssemblyExample");

            AssemblyBuilder ab =

                AppDomain.CurrentDomain.DefineDynamicAssembly(

                    aName,

                    AssemblyBuilderAccess.Run);

 

            // Create the module.

            ModuleBuilder mb = ab.DefineDynamicModule(aName.Name);

 

            TypeBuilder tb = mb.DefineType(

                "MyDynamicType",

                 TypeAttributes.Public);

 

            // Add a private field of type int (Int32).

            FieldBuilder fbNumber = tb.DefineField(

                "m_number",

                typeof(int),

                FieldAttributes.Private);

 

            // Define a constructor that takes an integer argument and

            // stores it in the private field.

            Type[] parameterTypes = { typeof(int) };

            ConstructorBuilder ctor1 = tb.DefineConstructor(

                MethodAttributes.Public,

                CallingConventions.Standard,

                parameterTypes);

 

            ILGenerator ctor1IL = ctor1.GetILGenerator();

            // For a constructor, argument zero is a reference to the new

            // instance. Push it on the stack before calling the base

            // class constructor. Specify the default constructor of the

            // base class (System.Object) by passing an empty array of

            // types (Type.EmptyTypes) to GetConstructor.

            ctor1IL.Emit(OpCodes.Ldarg_0);

            ctor1IL.Emit(OpCodes.Call,

                typeof(object).GetConstructor(Type.EmptyTypes));

            // Push the instance on the stack before pushing the argument

            // that is to be assigned to the private field m_number.

            ctor1IL.Emit(OpCodes.Ldarg_0);

            ctor1IL.Emit(OpCodes.Ldarg_1);

            ctor1IL.Emit(OpCodes.Stfld, fbNumber);

            ctor1IL.Emit(OpCodes.Ret);

 

            // Define a default constructor that supplies a default value

            // for the private field. For parameter types, pass the empty

            // array of types or pass null.

            ConstructorBuilder ctor0 = tb.DefineConstructor(

                MethodAttributes.Public,

                CallingConventions.Standard,

                Type.EmptyTypes);

 

            ILGenerator ctor0IL = ctor0.GetILGenerator();

            // For a constructor, argument zero is a reference to the new

            // instance. Push it on the stack before pushing the default

            // value on the stack, then call constructor ctor1.

            ctor0IL.Emit(OpCodes.Ldarg_0);

            ctor0IL.Emit(OpCodes.Ldc_I4_S, 42);

            ctor0IL.Emit(OpCodes.Call, ctor1);

            ctor0IL.Emit(OpCodes.Ret);

 

            // Define a property named Number that gets and sets the private

            // field.

            //

            // The last argument of DefineProperty is null, because the

            // property has no parameters. (If you don't specify null, you must

            // specify an array of Type objects. For a parameterless property,

            // use the built-in array with no elements: Type.EmptyTypes)

            PropertyBuilder pbNumber = tb.DefineProperty(

                "Number",

                PropertyAttributes.HasDefault,

                typeof(int),

                null);

 

            // The property "set" and property "get" methods require a special

            // set of attributes.

            MethodAttributes getSetAttr = MethodAttributes.Public |

                MethodAttributes.SpecialName | MethodAttributes.HideBySig;

 

            // Define the "get" accessor method for Number. The method returns

            // an integer and has no arguments. (Note that null could be

            // used instead of Types.EmptyTypes)

            MethodBuilder mbNumberGetAccessor = tb.DefineMethod(

                "get_Number",

                getSetAttr,

                typeof(int),

                Type.EmptyTypes);

 

            ILGenerator numberGetIL = mbNumberGetAccessor.GetILGenerator();

            // For an instance property, argument zero is the instance. Load the

            // instance, then load the private field and return, leaving the

            // field value on the stack.

            numberGetIL.Emit(OpCodes.Ldarg_0);

            numberGetIL.Emit(OpCodes.Ldfld, fbNumber);

            numberGetIL.Emit(OpCodes.Ret);

 

            // Define the "set" accessor method for Number, which has no return

            // type and takes one argument of type int (Int32).

            MethodBuilder mbNumberSetAccessor = tb.DefineMethod(

                "set_Number",

                getSetAttr,

                null,

                new Type[] { typeof(int) });

 

            ILGenerator numberSetIL = mbNumberSetAccessor.GetILGenerator();

            // Load the instance and then the numeric argument, then store the

            // argument in the field.

            numberSetIL.Emit(OpCodes.Ldarg_0);

            numberSetIL.Emit(OpCodes.Ldarg_1);

            numberSetIL.Emit(OpCodes.Stfld, fbNumber);

            numberSetIL.Emit(OpCodes.Ret);

 

            // Last, map the "get" and "set" accessor methods to the

            // PropertyBuilder. The property is now complete.

            pbNumber.SetGetMethod(mbNumberGetAccessor);

            pbNumber.SetSetMethod(mbNumberSetAccessor);

 

            // Define a method that accepts an integer argument and returns

            // the product of that integer and the private field m_number. This

            // time, the array of parameter types is created on the fly.

            MethodBuilder meth = tb.DefineMethod(

                "MyMethod",

                MethodAttributes.Public,

                typeof(int),

                new Type[] { typeof(int) });

 

            ILGenerator methIL = meth.GetILGenerator();

            // To retrieve the private instance field, load the instance it

            // belongs to (argument zero). After loading the field, load the

            // argument one and then multiply. Return from the method with

            // the return value (the product of the two numbers) on the

            // execution stack.

            methIL.Emit(OpCodes.Ldarg_0);

            methIL.Emit(OpCodes.Ldfld, fbNumber);

            methIL.Emit(OpCodes.Ldarg_1);

            methIL.Emit(OpCodes.Mul);

            methIL.Emit(OpCodes.Ret);

 

            // Finish the type.

            Type t = tb.CreateType();

 

            // The code can be executed immediately. Start by getting reflection

            // objects for the method and the property.

            MethodInfo mi = t.GetMethod("MyMethod");

            PropertyInfo pi = t.GetProperty("Number");

 

            // Create an instance of MyDynamicType using the default

            // constructor.

            object o1 = Activator.CreateInstance(t);

 

            // Display the value of the property, then change it to 127 and

            // display it again. Use null to indicate that the property

            // has no index.

            outputBlock.Text += String.Format("o1.Number: {0}\n", pi.GetValue(o1, null));

            pi.SetValue(o1, 127, null);

            outputBlock.Text += String.Format("o1.Number: {0}\n", pi.GetValue(o1, null));

 

            // Call MyMethod, passing 22, and display the return value, 22

            // times 127. Arguments must be passed as an array, even when

            // there is only one.

            object[] arguments = { 22 };

            outputBlock.Text += String.Format("o1.MyMethod(22): {0}\n",

                mi.Invoke(o1, arguments));

 

            // Create an instance of MyDynamicType using the constructor

            // that specifies m_Number. The constructor is identified by

            // matching the types in the argument array. In this case,

            // the argument array is created on the fly. Display the

            // property value.

            object o2 = Activator.CreateInstance(t,

                new object[] { 5280 });

            outputBlock.Text += String.Format("o2.Number: {0}\n", pi.GetValue(o2, null));

        }

    }