Поделиться через


Type.GetProperty Method (String, Type, array<Type[], array<ParameterModifier[])

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

Searches for the specified public property whose parameters match the specified argument types and modifiers.

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

Syntax

'Declaration
Public Function GetProperty ( _
    name As String, _
    returnType As Type, _
    types As Type(), _
    modifiers As ParameterModifier() _
) As PropertyInfo
public PropertyInfo GetProperty(
    string name,
    Type returnType,
    Type[] types,
    ParameterModifier[] modifiers
)

Parameters

  • returnType
    Type: System.Type
    The return type of the property.
  • types
    Type: array<System.Type[]
    An array of Type objects representing the number, order, and type of the parameters for the indexed property to get.
    -or-
    An empty array of the type Type (that is, Type[] types = new Type[0]) to get a property that is not indexed.

Return Value

Type: System.Reflection.PropertyInfo
A PropertyInfo object representing the public property that matches the specified requirements, if found; otherwise, nulla null reference (Nothing in Visual Basic).

Exceptions

Exception Condition
AmbiguousMatchException

More than one property is found with the specified name and matching the specified argument types and modifiers.

ArgumentNullException

name is nulla null reference (Nothing in Visual Basic).

-or-

types is nulla null reference (Nothing in Visual Basic).

ArgumentException

types is multidimensional.

-or-

modifiers is multidimensional.

-or-

types and modifiers do not have the same length.

NullReferenceException

An element of types is nulla null reference (Nothing in Visual Basic).

Remarks

A property is considered public to reflection if it has at least one accessor that is public. Otherwise the property is considered private, and you must use BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static (in Visual Basic, combine the values using Or) to get it.

Although the default binder does not process ParameterModifier (the modifiers parameter), you can use the abstract System.Reflection.Binder class to write a custom binder that does process modifiers. ParameterModifier is only used when calling through COM interop, and only parameters that are passed by reference are handled.

The types array and the modifiers array have the same length. A parameter specified in the types array can have the following attributes, which are specified in the modifiers array: pdIn, pdOut, pdLcid, pdRetval, pdOptional, and pdHasDefault, which represent [In], [Out], [lcid], [retval], [optional], and a value specifying whether the parameter has a default value. A parameter's associated attributes are stored in the metadata and enhance interoperability.

The search for name is case-sensitive. The search includes public static and public instance properties.

If the current Type represents a constructed generic type, this method returns the PropertyInfo with the type parameters replaced by the appropriate type arguments.

If the current Type represents a type parameter in the definition of a generic type or generic method, this method searches the properties of the class constraint.

Indexers and Default Properties

Visual Basic 2005, Visual C# 2005, and Visual C++ 2005 have simplified syntax for accessing indexed properties and allow one indexed property to be a default for its type. For example, if the variable myList refers to a List<T>, the syntax myList[3] (myList(3) in Visual Basic) retrieves the element with the index of 3. You can overload the property.

In C#, this feature is called an indexer and cannot be refered to by name. By default, a C# indexer appears in metadata as an indexed property named "Item". However, a class library developer can use the IndexerNameAttribute attribute to change the name of the indexer in the metadata. For example, the String class has an indexer named Chars. Indexed properties created using languages other than C# can have names other than Item, as well. 

To determine whether a type has a default property, use the GetCustomAttributes(Type, Boolean) method to test for the DefaultMemberAttribute attribute. If the type has DefaultMemberAttribute, the MemberName property returns the name of the default property.

Platform Notes

Silverlight for Windows Phone Silverlight for Windows Phone

 GetProperty throws NullReferenceException instead of ArgumentNullException when types contains a nulla null reference (Nothing in Visual Basic) element.

Examples

The following example obtains a Type object corresponding to MyPropertyClass, and the indexed property of this class is retrieved using the arguments passed to the GetProperty method.

Imports System.Reflection

Public Class MyPropertyClass
   Private myPropertyArray(9, 9) As Integer
   ' Declare an indexer.
   Default Public Property Item(ByVal i As Integer, ByVal j As Integer) As Integer
      Get
         Return myPropertyArray(i, j)
      End Get
      Set(ByVal Value As Integer)
         myPropertyArray(i, j) = Value
      End Set
   End Property
End Class 'MyPropertyClass

Public Class Example
   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Try
         Dim myType As Type = GetType(MyPropertyClass)
         Dim myTypeArray(1) As Type
         ' Create an instance of a Type array representing the number, order 
         ' and type of the parameters for the property.
         myTypeArray.SetValue(GetType(Integer), 0)
         myTypeArray.SetValue(GetType(Integer), 1)
         ' Search for the indexed property whose parameters match the
         ' specified argument types and modifiers.
         Dim myPropertyInfo As PropertyInfo = myType.GetProperty("Item", _
               GetType(Integer), myTypeArray, Nothing)
         outputBlock.Text &= myType.FullName + "." + myPropertyInfo.Name + _
               " has a property  type of " + myPropertyInfo.PropertyType.ToString() & vbCrLf
      Catch ex As Exception
         outputBlock.Text &= "An exception occurred " + ex.Message.ToString() & vbCrLf
      End Try
   End Sub 'Main
End Class 'MyTypeClass
using System;
using System.Reflection;
public class MyPropertyClass
{
   private int[,] myPropertyArray = new int[10, 10];
   // Declare an indexer.
   public int this[int i, int j]
   {
      get
      {
         return myPropertyArray[i, j];
      }
      set
      {
         myPropertyArray[i, j] = value;
      }
   }
}
public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      try
      {
         Type myType = typeof(MyPropertyClass);
         Type[] myTypeArray = new Type[2];
         // Create an instance of the Type array representing the number, order 
         // and type of the parameters for the property.
         myTypeArray.SetValue(typeof(int), 0);
         myTypeArray.SetValue(typeof(int), 1);
         // Search for the indexed property whose parameters match the
         // specified argument types and modifiers.
         PropertyInfo myPropertyInfo = myType.GetProperty("Item",
             typeof(int), myTypeArray, null);
         outputBlock.Text += myType.FullName + "." + myPropertyInfo.Name +
             " has a property type of " + myPropertyInfo.PropertyType + "\n";
      }
      catch (Exception ex)
      {
         outputBlock.Text += "An exception occurred " + ex.Message + "\n";
      }
   }
}

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.