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11/18/2011

ParameterInfo Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Discovers the attributes of a parameter and provides access to parameter metadata.

Inheritance Hierarchy

System.Object
System.Reflection.ParameterInfo

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
<ClassInterfaceAttribute(ClassInterfaceType.None)> _
Public Class ParameterInfo _
    Implements ICustomAttributeProvider

[ComVisibleAttribute(true)]
[ClassInterfaceAttribute(ClassInterfaceType.None)]
public class ParameterInfo : ICustomAttributeProvider

The ParameterInfo type exposes the following members.

Constructors

	Name	Description
	ParameterInfo	Initializes a new instance of the ParameterInfo class.

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Properties

	Name	Description
	Attributes	Gets the attributes for this parameter.
	DefaultValue	Gets the default value, if the parameter has a default value.
	IsIn	Gets a value indicating whether this is an input parameter.
	IsOptional	Gets a value indicating whether this parameter is optional.
	IsOut	Gets a value indicating whether this is an output parameter.
	Member	Gets the member in which the parameter is defined.
	MetadataToken	Gets a value that identifies this parameter in metadata.
	Name	Gets the name of the parameter.
	ParameterType	Gets the type of this parameter.
	Position	Gets the zero-based position of the parameter in the formal parameter list.
	RawDefaultValue	Gets a value indicating the default value if the parameter has a default value.

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Methods

	Name	Description
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.) In Silverlight for Windows Phone, this member is overridden by Equals(Object). In XNA Framework, this member is overridden by Equals(Object).
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetCustomAttributes(Boolean)	Gets all the custom attributes defined on this parameter.
	GetCustomAttributes(Type, Boolean)	Gets the custom attributes of the specified type or its derived types that are applied to this parameter.
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.) In Silverlight for Windows Phone, this member is overridden by GetHashCode(). In XNA Framework, this member is overridden by GetHashCode().
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	IsDefined	Determines whether the custom attribute of the specified type or its derived types is applied to this parameter.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Gets the parameter type and name represented as a string. (Overrides Object.ToString().)

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Remarks

Use an instance of ParameterInfo to obtain information about the parameter's data type, default value, and so on.

MethodBase.GetParameters returns an array of ParameterInfo objects representing the parameters of a method, in order.

Examples

The following example defines a method with four parameters and uses the ParameterInfo.Attributes property to display the attributes of the parameters.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

Imports System.Reflection
Imports System.Runtime.InteropServices

Class Example

   Public Shared Sub mymethod(ByVal str1 As String, ByRef str2 As String, _
      <Out> ByRef str3 As String, <InAttribute> ByVal str4 As String)

      ' Add str1 to str2, which is ByRef.
      str2 &= str1
      ' When mymethod is called, str3 has no value. Give it one.
      str3 = "new value"
   End Sub

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) 

      ' Get the method.
      Dim mm As MethodInfo = GetType(Example).GetMethod("mymethod")

      ' Display the method.
      outputBlock.Text &= "MethodInfo.ToString(): " & mm.ToString() & vbCrLf

      For Each param In mm.GetParameters()

         outputBlock.Text &= String.Format("Attributes for parameter {0}, ""{1}"": {2} ({3})", _ 
            param.Position, param.Name, param.Attributes, CInt(param.Attributes))

         If param.ParameterType.IsByRef Then
            outputBlock.Text &= "; the parameter type is ByRef" & vbLf
         Else
            outputBlock.Text &= vbLf
         End If
      Next
   End Sub
End Class

' This code produces the following output:
'
'MethodInfo.ToString(): Void mymethod(System.String, System.String ByRef, System.String ByRef)
'Attributes for parameter 0, "str1": None (0)
'Attributes for parameter 1, "str2": None (0); the parameter type is ByRef
'Attributes for parameter 2, "str3": Out (2); the parameter type is ByRef
'Attributes for parameter 3, "str4": In (1)

using System;
using System.Reflection;
using System.Runtime.InteropServices;

class Example
{
   public static void mymethod(string str1, ref string str2, out string str3,
      [In] string str4)
   {
      // Concatenate str1 to str2, which is ref.
      str2 += str1;
      // When mymethod is called, str3 has no value. Give it one.
      str3 = "new value";
   }

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      MethodInfo mm = typeof(Example).GetMethod("mymethod");

      // Display the method.
      outputBlock.Text += "MethodInfo.ToString(): " + mm.ToString() + "\n";

      // Get and display the attributes for the second parameter.
      foreach (ParameterInfo param in mm.GetParameters())
      {
         outputBlock.Text += String.Format("Attributes for parameter {0}, \"{1}\": {2} ({3})",  
            param.Position, param.Name, param.Attributes, (int)param.Attributes);

         if (param.ParameterType.IsByRef)
         {
            outputBlock.Text += "; the parameter type is ref\n";
         }
         else
         {
            outputBlock.Text += "\n";
         }
      }
   }
}

/* This code produces the following output:

MethodInfo.ToString(): Void mymethod(System.String, System.String ByRef, System.String ByRef)
Attributes for parameter 0, "str1": None (0)
Attributes for parameter 1, "str2": None (0); the parameter type is ByRef
Attributes for parameter 2, "str3": Out (2); the parameter type is ByRef
Attributes for parameter 3, "str4": In (1)
 */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

This type is thread safe.

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