.NET Framework Class Library
ReadOnlyAttribute Class

Specifies whether the property this attribute is bound to is read-only or read/write. This class cannot be inherited

Inheritance Hierarchy
SystemObject
   SystemAttribute
    System.ComponentModelReadOnlyAttribute

Namespace:   System.ComponentModel
Assembly:  System (in System.dll)
Syntax
<[%$TOPIC/yhbfx50t_en-us_VS_110_2_0_0_0_0%]([%$TOPIC/yhbfx50t_en-us_VS_110_2_0_0_0_1%].All)> _
Public NotInheritable Class ReadOnlyAttribute _
	Inherits [%$TOPIC/yhbfx50t_en-us_VS_110_2_0_0_0_2%]
[[%$TOPIC/yhbfx50t_en-us_VS_110_2_0_1_0_0%]([%$TOPIC/yhbfx50t_en-us_VS_110_2_0_1_0_1%].All)]
public sealed class ReadOnlyAttribute : [%$TOPIC/yhbfx50t_en-us_VS_110_2_0_1_0_2%]
[[%$TOPIC/yhbfx50t_en-us_VS_110_2_0_2_0_0%]([%$TOPIC/yhbfx50t_en-us_VS_110_2_0_2_0_1%]::All)]
public ref class ReadOnlyAttribute sealed : public [%$TOPIC/yhbfx50t_en-us_VS_110_2_0_2_0_2%]
[<[%$TOPIC/yhbfx50t_en-us_VS_110_2_0_3_0_0%]>]
[<[%$TOPIC/yhbfx50t_en-us_VS_110_2_0_3_0_1%]([%$TOPIC/yhbfx50t_en-us_VS_110_2_0_3_0_2%].All)>]
type ReadOnlyAttribute =  
    class 
        inherit [%$TOPIC/yhbfx50t_en-us_VS_110_2_0_3_0_3%] 
    end
public final class ReadOnlyAttribute extends [%$TOPIC/yhbfx50t_en-us_VS_110_2_0_4_0_0%]

The ReadOnlyAttribute type exposes the following members.

Constructors
  NameDescription
Public method ReadOnlyAttributeInitializes a new instance of the ReadOnlyAttribute class.
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Properties
  NameDescription
Public property IsReadOnlyGets a value indicating whether the property this attribute is bound to is read-only.
Public property TypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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Methods
  NameDescription
Public method EqualsIndicates whether this instance and a specified object are equal. (Overrides AttributeEquals(Object).)
Public method GetHashCodeReturns the hash code for this instance. (Overrides AttributeGetHashCode.)
Public method GetTypeGets the Type of the current instance. (Inherited from Object.)
Public method IsDefaultAttributeDetermines if this attribute is the default. (Overrides AttributeIsDefaultAttribute.)
Public method MatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public method ToStringReturns a string that represents the current object. (Inherited from Object.)
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Fields
  NameDescription
Public field Static member DefaultSpecifies the default value for the ReadOnlyAttribute, which is No (that is, the property this attribute is bound to is read/write). This static field is read-only.
Public field Static member NoSpecifies that the property this attribute is bound to is read/write and can be modified. This static field is read-only.
Public field Static member YesSpecifies that the property this attribute is bound to is read-only and cannot be modified in the server explorer. This static field is read-only.
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Explicit Interface Implementations
  NameDescription
Explicit interface implemetation Private method _AttributeGetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetation Private method _AttributeGetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetation Private method _AttributeGetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetation Private method _AttributeInvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)
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Remarks

Members that are marked with the ReadOnlyAttribute set to true or that do not have a Set method cannot be changed. Members that do not have this attribute or that are marked with the ReadOnlyAttribute set to false are read/write, and they can be changed. The default is No.

Important noteImportant

The PropertyDescriptor class enforces the ReadOnlyAttribute in the design environment and at run time. When you mark a property with the ReadOnlyAttribute set to true, the value of this attribute is set to the constant member Yes. For a property marked with the ReadOnlyAttribute set to false, the value is No. Therefore, when you want to check the value of this attribute in your code, you must specify the attribute as ReadOnlyAttributeYes or ReadOnlyAttributeNo.

For more information, see Extending Metadata Using Attributes.

Examples

The following code example marks a property as read-only.

Public ReadOnly Property MyProperty() As Integer 
    Get 
        ' Insert code here. 
        Return 0
    End Get 
End Property
[ReadOnly(true)]
 public int MyProperty {
    get {
       // Insert code here. 
       return 0;
    }
}
   [ReadOnly(true)]
   int get()
   {
      // Insert code here. 
      return 0;
   }
}

The next code example shows how to check the value of the ReadOnlyAttribute for MyProperty. First, the code gets a PropertyDescriptorCollection with all the properties for the object. Next, it indexes into the PropertyDescriptorCollection to get MyProperty. Then it returns the attributes for this property and saves them in the attributes variable.

The example presents two different ways of checking the value of the ReadOnlyAttribute. In the second code fragment, the example calls the Equals method. In the last code fragment, the example uses the IsReadOnly property to check the value.

' Gets the attributes for the property. 
Dim attributes As AttributeCollection = _
    TypeDescriptor.GetProperties(Me)("MyProperty").Attributes

' Checks to see whether the value of the ReadOnlyAttribute is Yes. 
If attributes(GetType(ReadOnlyAttribute)).Equals(ReadOnlyAttribute.Yes) Then 
    ' Insert code here. 
End If  

' This is another way to see whether the property is read-only. 
Dim myAttribute As ReadOnlyAttribute = _
    CType(attributes(GetType(ReadOnlyAttribute)), ReadOnlyAttribute)

If myAttribute.IsReadOnly Then 
    ' Insert code here. 
End If
// Gets the attributes for the property.
AttributeCollection attributes = 
   TypeDescriptor.GetProperties(this)["MyProperty"].Attributes;

// Checks to see whether the value of the ReadOnlyAttribute is Yes. 
if(attributes[typeof(ReadOnlyAttribute)].Equals(ReadOnlyAttribute.Yes)) {
   // Insert code here.
}

// This is another way to see whether the property is read-only.
ReadOnlyAttribute myAttribute = 
   (ReadOnlyAttribute)attributes[typeof(ReadOnlyAttribute)];
if(myAttribute.IsReadOnly) {
   // Insert code here.
}
// Gets the attributes for the property.
AttributeCollection^ attributes = TypeDescriptor::GetProperties( this )[ "MyProperty" ]->Attributes;

// Checks to see whether the value of the ReadOnlyAttribute is Yes. 
if ( attributes[ ReadOnlyAttribute::typeid ]->Equals( ReadOnlyAttribute::Yes ) )
{
   // Insert code here.
}

// This is another way to see whether the property is read-only.
ReadOnlyAttribute^ myAttribute = dynamic_cast<ReadOnlyAttribute^>(attributes[ ReadOnlyAttribute::typeid ]);
if ( myAttribute->IsReadOnly )
{
   // Insert code here.
}

If you marked a class with the ReadOnlyAttribute, use the following code example to check the value.

Dim attributes As AttributeCollection = TypeDescriptor.GetAttributes(MyProperty)
If attributes(GetType(ReadOnlyAttribute)).Equals(ReadOnlyAttribute.Yes) Then 
    ' Insert code here. 
End If
AttributeCollection attributes = 
   TypeDescriptor.GetAttributes(MyProperty);
if(attributes[typeof(ReadOnlyAttribute)].Equals(ReadOnlyAttribute.Yes)) {
   // Insert code here.
}
AttributeCollection^ attributes = TypeDescriptor::GetAttributes( MyProperty );
if ( attributes[ ReadOnlyAttribute::typeid ]->Equals( ReadOnlyAttribute::Yes ) )
{
   // Insert code here.
}
Version Information

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

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