对于Binder的重载是为了进行动态调用方法的类型转换。
using System;using System.Reflection;using System.Globalization;// 从候选者列表中选择一个成员，并执行实参类型到形参类型的类型转换
#region MyBinder
public class MyBinder : Binder 
{
public MyBinder() : base() {
} private class BinderState { public object[] args; } public override FieldInfo BindToField( BindingFlags bindingAttr, FieldInfo[] match, object value, CultureInfo culture ) { if(match == null) throw new ArgumentNullException("match"); // Get a field for which the value parameter can be converted to the specified field type. for(int i = 0; i < match.Length; i++) if(ChangeType(value, match[i].FieldType, culture) != null) return match[i]; return null; } public override MethodBase BindToMethod( BindingFlags bindingAttr, MethodBase[] match, ref object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] names, out object state ) { // Store the arguments to the method in a state object. BinderState myBinderState = new BinderState(); object[] arguments = new Object[args.Length]; args.CopyTo(arguments, 0); myBinderState.args = arguments; state = myBinderState; if(match == null) throw new ArgumentNullException(); // Find a method that has the same parameters as those of the args parameter. for(int i = 0; i < match.Length; i++) { // Count the number of parameters that match. int count = 0; ParameterInfo[] parameters = match[i].GetParameters(); // Go on to the next method if the number of parameters do not match. if(args.Length != parameters.Length) continue; // Match each of the parameters that the user expects the method to have. for(int j = 0; j < args.Length; j++) { // If the names parameter is not null, then reorder args. if(names != null) { if(names.Length != args.Length) throw new ArgumentException("names and args must have the same number of elements."); for(int k = 0; k < names.Length; k++) if(String.Compare(parameters[j].Name, names[k].ToString()) == 0) args[j] = myBinderState.args[k]; } // Determine whether the types specified by the user can be converted to the parameter type. if(ChangeType(args[j], parameters[j].ParameterType, culture) != null) count += 1; else break; } // Determine whether the method has been found. if(count == args.Length) return match[i]; } return null; } public override object ChangeType( object value, Type myChangeType, CultureInfo culture ) { // Determine whether the value parameter can be converted to a value of type myType. if(CanConvertFrom(value.GetType(), myChangeType)) //public static System.Object ChangeType ( System.Object value , System.Type conversionType , System.IFormatProvider provider ) // Return the converted object.返回具有指定 System.Type 而且其值等效于指定对象的 System.Object。参数提供区域性特定的格式设置信息。 return Convert.ChangeType(value, myChangeType); else // Return null. return null; } public override void ReorderArgumentArray( ref object[] args, object state ) { // Return the args that had been reordered by BindToMethod. ((BinderState)state).args.CopyTo(args, 0); } public override MethodBase SelectMethod( BindingFlags bindingAttr, MethodBase[] match, Type[] types, ParameterModifier[] modifiers ) { if(match == null) throw new ArgumentNullException("match"); for(int i = 0; i < match.Length; i++) { // Count the number of parameters that match. int count = 0; ParameterInfo[] parameters = match[i].GetParameters(); // Go on to the next method if the number of parameters do not match. if(types.Length != parameters.Length) continue; // Match each of the parameters that the user expects the method to have. for(int j = 0; j < types.Length; j++) // Determine whether the types specified by the user can be converted to parameter type. if(CanConvertFrom(types[j], parameters[j].ParameterType)) count += 1; else break; // Determine whether the method has been found. if(count == types.Length) return match[i]; } return null; } public override PropertyInfo SelectProperty( BindingFlags bindingAttr, PropertyInfo[] match, Type returnType, Type[] indexes, ParameterModifier[] modifiers ) { if(match == null) throw new ArgumentNullException("match"); for(int i = 0; i < match.Length; i++) { // Count the number of indexes that match. int count = 0; ParameterInfo[] parameters = match[i].GetIndexParameters(); // Go on to the next property if the number of indexes do not match. if(indexes.Length != parameters.Length) continue; // Match each of the indexes that the user expects the property to have. for(int j = 0; j < indexes.Length; j++) // Determine whether the types specified by the user can be converted to index type. if(CanConvertFrom(indexes[j], parameters[j].ParameterType)) count += 1; else break; // Determine whether the property has been found. if(count == indexes.Length) // Determine whether the return type can be converted to the properties type. if(CanConvertFrom(returnType, match[i].GetType())) return match[i]; else continue; } return null; } #region Determines whether type1 can be converted to type2. Check only for primitive types. private bool CanConvertFrom(Type type1, Type type2) { if(type1.IsPrimitive && type2.IsPrimitive) { TypeCode typeCode1 = Type.GetTypeCode(type1); TypeCode typeCode2 = Type.GetTypeCode(type2); // If both type1 and type2 have the same type, return true. if(typeCode1 == typeCode2) return true; // Possible conversions from Char follow. if(typeCode1 == TypeCode.Char) switch(typeCode2) { case TypeCode.UInt16 : return true; case TypeCode.UInt32 : return true; case TypeCode.Int32 : return true; case TypeCode.UInt64 : return true; case TypeCode.Int64 : return true; case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from Byte follow. if(typeCode1 == TypeCode.Byte) switch(typeCode2) { case TypeCode.Char : return true; case TypeCode.UInt16 : return true; case TypeCode.Int16 : return true; case TypeCode.UInt32 : return true; case TypeCode.Int32 : return true; case TypeCode.UInt64 : return true; case TypeCode.Int64 : return true; case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from SByte follow. if(typeCode1 == TypeCode.SByte) switch(typeCode2) { case TypeCode.Int16 : return true; case TypeCode.Int32 : return true; case TypeCode.Int64 : return true; case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from UInt16 follow. if(typeCode1 == TypeCode.UInt16) switch(typeCode2) { case TypeCode.UInt32 : return true; case TypeCode.Int32 : return true; case TypeCode.UInt64 : return true; case TypeCode.Int64 : return true; case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from Int16 follow. if(typeCode1 == TypeCode.Int16) switch(typeCode2) { case TypeCode.Int32 : return true; case TypeCode.Int64 : return true; case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from UInt32 follow. if(typeCode1 == TypeCode.UInt32) switch(typeCode2) { case TypeCode.UInt64 : return true; case TypeCode.Int64 : return true; case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from Int32 follow. if(typeCode1 == TypeCode.Int32) switch(typeCode2) { case TypeCode.Int64 : return true; case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from UInt64 follow. if(typeCode1 == TypeCode.UInt64) switch(typeCode2) { case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from Int64 follow. if(typeCode1 == TypeCode.Int64) switch(typeCode2) { case TypeCode.Single : return true; case TypeCode.Double : return true; default : return false; } // Possible conversions from Single follow. if(typeCode1 == TypeCode.Single) switch(typeCode2) { case TypeCode.Double : return true; default : return false; } } return false; } #endregion}
#endregion#region MyClass1public class MyClass1{ public short myFieldB; public int myFieldA; public void MyMethod(long i, char k) { Console.WriteLine("\nThis is MyMethod(long i, char k)"); } public void MyMethod(long i, long j) { Console.WriteLine("\nThis is MyMethod(long i, long j)"); }}public class Binder_Example{ public static void Main() { // Get the type of MyClass1. Type myType = typeof(MyClass1); // Get the instance of MyClass1. MyClass1 myInstance = new MyClass1(); Console.WriteLine("\nDisplaying the results of using the MyBinder binder.\n"); // Get the method information for MyMethod. SelectMethod() MethodInfo myMethod = myType.GetMethod("MyMethod", BindingFlags.Public | BindingFlags.Instance, new MyBinder(), new Type[] {typeof(short), typeof(short)}, null); Console.WriteLine(myMethod); // Invoke MyMethod. ChangeType() myMethod.Invoke(myInstance, BindingFlags.InvokeMethod, new MyBinder(), new Object[] {(int)32, (int)32}, CultureInfo.CurrentCulture); Console.ReadLine(); }}#endregion
