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Binder Class

Selects a member from a list of candidates, and performs type conversion from actual argument type to formal argument type.

System.Object
  System.Reflection.Binder

Namespace:  System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

[SerializableAttribute]
[ComVisibleAttribute(true)]
[ClassInterfaceAttribute(ClassInterfaceType.AutoDual)]
public abstract class Binder

The Binder type exposes the following members.

  NameDescription
Protected methodSupported by the XNA FrameworkBinderInitializes a new instance of the Binder class.
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  NameDescription
Public methodSupported by the XNA FrameworkBindToFieldSelects a field from the given set of fields, based on the specified criteria.
Public methodSupported by the XNA FrameworkBindToMethodSelects a method to invoke from the given set of methods, based on the supplied arguments.
Public methodSupported by the XNA FrameworkChangeTypeChanges the type of the given Object to the given Type.
Public methodSupported by the XNA FrameworkEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodSupported by the XNA FrameworkFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by the XNA FrameworkGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodSupported by the XNA FrameworkGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by the XNA FrameworkMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by the XNA FrameworkReorderArgumentArrayUpon returning from BindToMethod, restores the args argument to what it was when it came from BindToMethod.
Public methodSupported by the XNA FrameworkSelectMethodSelects a method from the given set of methods, based on the argument type.
Public methodSupported by the XNA FrameworkSelectPropertySelects a property from the given set of properties, based on the specified criteria.
Public methodSupported by the XNA FrameworkToStringReturns a string that represents the current object. (Inherited from Object.)
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Implementations of the Binder class are used by methods such as Type.InvokeMember, which selects from a set of possible members to execute, based on a set of parameter types and argument values; Type.GetMethod, which selects a method based on parameter types; and so on.

A default implementation of the Binder class is provided by the Type.DefaultBinder property.

Notes to Inheritors

When you inherit from Binder, you must override the following members: BindToMethod, BindToField, ReorderArgumentArray, SelectMethod, SelectProperty, and ChangeType.

The following example implements and demonstrates all members of the Binder class. The private method CanConvertFrom finds compatible types for a given type.

using System;
using System.Reflection;
using System.Globalization;

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))
            // Return the converted object. 
            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].PropertyType))
                    return match[i];
                else 
                    continue;
        }
        return null;
    }
    // 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;
    }
}
public 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.
        MethodInfo myMethod = myType.GetMethod("MyMethod", BindingFlags.Public | BindingFlags.Instance,
            new MyBinder(), new Type[] {typeof(short), typeof(short)}, null);
        Console.WriteLine(myMethod);
        // Invoke MyMethod.
        myMethod.Invoke(myInstance, BindingFlags.InvokeMethod, new MyBinder(), new Object[] {(int)32, (int)32}, CultureInfo.CurrentCulture);
    }
}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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