[原创]Silverlight中动态数据验证和动态自动计算的Reflection反射实现
2011-06-25 17:53
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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
class Example
{
publicstaticvoid 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,
newobject[] { 5280 });
outputBlock.Text += String.Format("o2.Number: {0}\n", pi.GetValue(o2, null));
}
}
好了,原理清晰了,一起看看在Siverlight上实现的例子吧(一定要看最后一节的“动态自定义验证”),感谢大家。
在线演示(ver2011):
http://crmwin.com/FreeForm2011TestPage.html
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