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ReadOnlyAttribute Class

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

System.Object
  System.Attribute
    System.ComponentModel.ReadOnlyAttribute

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

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

The ReadOnlyAttribute type exposes the following members.

  NameDescription
Public methodReadOnlyAttributeInitializes a new instance of the ReadOnlyAttribute class.
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  NameDescription
Public propertyIsReadOnlyGets a value indicating whether the property this attribute is bound to is read-only.
Public propertyTypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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  NameDescription
Public methodEqualsIndicates whether this instance and a specified object are equal. (Overrides Attribute.Equals(Object).)
Public methodGetHashCodeReturns the hash code for this instance. (Overrides Attribute.GetHashCode().)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeDetermines if this attribute is the default. (Overrides Attribute.IsDefaultAttribute().)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Public fieldStatic memberDefaultSpecifies 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 fieldStatic memberNoSpecifies that the property this attribute is bound to is read/write and can be modified. This static field is read-only.
Public fieldStatic memberYesSpecifies 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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  NameDescription
Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)
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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 ReadOnlyAttribute.Yes or ReadOnlyAttribute.No.

For more information, see 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;
    }
}

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.
}

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.
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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