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ReadOnlyAttribute Class

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

Namespace: System.ComponentModel
Assembly: System (in system.dll)

[AttributeUsageAttribute(AttributeTargets.All)] 
public sealed class ReadOnlyAttribute : Attribute
/** @attribute AttributeUsageAttribute(AttributeTargets.All) */ 
public final class ReadOnlyAttribute extends Attribute
AttributeUsageAttribute(AttributeTargets.All) 
public final class ReadOnlyAttribute extends Attribute
Not applicable.

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.

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 ReadOnlyAttribute.Yes or ReadOnlyAttribute.No.

For more information, see Attributes Overview and Extending Metadata Using Attributes.

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

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

/** @attribute ReadOnly(true)
 */
/** @property 
 */
public int get_MyProperty()
{
    // Insert code here.
    return 0;
} //get_MyProperty

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[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).
    get_Item("MyProperty").get_Attributes();

// Checks to see whether the value of the ReadOnlyAttribute is Yes.
if (attributes.get_Item(ReadOnlyAttribute.class.ToType()).Equals
    (ReadOnlyAttribute.Yes)) {
    // Insert code here.
}

// This is another way to see whether the property is read-only.
ReadOnlyAttribute myAttribute = ((ReadOnlyAttribute)
    (attributes.get_Item(ReadOnlyAttribute.class.ToType())));

if (myAttribute.get_IsReadOnly()) {
    // Insert code here.
}

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

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

AttributeCollection attributes = 
    TypeDescriptor.GetAttributes("MyProperty");

if (attributes.get_Item(ReadOnlyAttribute.class.ToType()).Equals(
    ReadOnlyAttribute.Yes)) {
    // Insert code here.
}

System.Object
   System.Attribute
    System.ComponentModel.ReadOnlyAttribute

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

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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