ReadOnlyAttribute Class

Definition

Namespace:

System.ComponentModel

Assembly:

System.ComponentModel.Primitives.dll

Source:

ReadOnlyAttribute.cs

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

public ref class ReadOnlyAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.All)]
public sealed class ReadOnlyAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.All)>]
type ReadOnlyAttribute = class
    inherit Attribute

Public NotInheritable Class ReadOnlyAttribute
Inherits Attribute

Inheritance

Object

Attribute

ReadOnlyAttribute

Attributes

AttributeUsageAttribute

Examples

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

   [ReadOnly(true)]
   int get()
   {
      // Insert code here.
      return 0;
   }
}

[ReadOnly(true)]
 public int MyProperty {
    get {
       // Insert code here.
       return 0;
    }
}

Public ReadOnly Property MyProperty() As Integer
    Get
        ' Insert code here.
        Return 0
    End Get
End Property

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.
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.
}

// 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.
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

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

AttributeCollection^ attributes = TypeDescriptor::GetAttributes( MyProperty );
if ( attributes[ ReadOnlyAttribute::typeid ]->Equals( ReadOnlyAttribute::Yes ) )
{
   // Insert code here.
}

AttributeCollection attributes = 
   TypeDescriptor.GetAttributes(MyProperty);
if(attributes[typeof(ReadOnlyAttribute)].Equals(ReadOnlyAttribute.Yes)) {
   // Insert code here.
}

Dim attributes As AttributeCollection = TypeDescriptor.GetAttributes(MyProperty)
If attributes(GetType(ReadOnlyAttribute)).Equals(ReadOnlyAttribute.Yes) Then
    ' Insert code here.
End If

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

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 ReadOnlyAttribute.Yes or ReadOnlyAttribute.No.

For more information, see Attributes.

Constructors

ReadOnlyAttribute(Boolean)

Initializes a new instance of the ReadOnlyAttribute class.

Fields

Default	Specifies 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.
No	Specifies that the property this attribute is bound to is read/write and can be modified. This static field is read-only.
Yes	Specifies 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.

Properties

IsReadOnly	Gets a value indicating whether the property this attribute is bound to is read-only.
TypeId	When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute)

Methods

Equals(Object)	Indicates whether this instance and a specified object are equal.
GetHashCode()	Returns the hash code for this instance.
GetType()	Gets the Type of the current instance. (Inherited from Object)
IsDefaultAttribute()	Determines if this attribute is the default.
Match(Object)	When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

See also

• Attribute
• PropertyDescriptor
• AttributeCollection
• PropertyDescriptorCollection