RequiredAttribute Class
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Specifies that a value must be provided for a property.
Inheritance Hierarchy
System.Object
System.Attribute
System.ComponentModel.DataAnnotations.ValidationAttribute
System.ComponentModel.DataAnnotations.RequiredAttribute
Namespace: System.ComponentModel.DataAnnotations
Assembly: System.ComponentModel.DataAnnotations (in System.ComponentModel.DataAnnotations.dll)
Syntax
'Declaration
<AttributeUsageAttribute(AttributeTargets.Property Or AttributeTargets.Field Or AttributeTargets.Parameter, AllowMultiple := False)> _
Public Class RequiredAttribute _
Inherits ValidationAttribute
[AttributeUsageAttribute(AttributeTargets.Property|AttributeTargets.Field|AttributeTargets.Parameter, AllowMultiple = false)]
public class RequiredAttribute : ValidationAttribute
The RequiredAttribute type exposes the following members.
Constructors
| Name | Description | |
|---|---|---|
.gif "Public method") |
RequiredAttribute | Initializes a new instance of the RequiredAttribute class. |
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Properties
| Name | Description | |
|---|---|---|
.gif "Public property") |
AllowEmptyStrings | Gets or sets a value that indicates whether an empty string is allowed. |
|
ErrorMessage | Gets or sets the non-localizable error message to display when validation fails. (Inherited from ValidationAttribute.) |
|
ErrorMessageResourceName | Gets or sets the property name on the resource type that provides the localizable error message. (Inherited from ValidationAttribute.) |
|
ErrorMessageResourceType | Gets or sets the resource type that provides the localizable error message. (Inherited from ValidationAttribute.) |
.gif "Protected property") |
ErrorMessageString | Gets the localized or non-localized error message. (Inherited from ValidationAttribute.) |
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Methods
| Name | Description | |
|---|---|---|
|
Equals | Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.) |
.gif "Protected method") |
Finalize | Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.) |
|
FormatErrorMessage | Applies formatting to the error message. (Inherited from ValidationAttribute.) |
|
GetHashCode | Returns the hash code for this instance. (Inherited from Attribute.) |
|
GetType | Gets the Type of the current instance. (Inherited from Object.) |
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GetValidationResult | Determines whether the specified object is valid and returns an object that includes the results of the validation check. (Inherited from ValidationAttribute.) |
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IsValid | Determines whether the specified object is valid. (Inherited from ValidationAttribute.) |
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Match | When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.) |
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MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
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ToString | Returns a string that represents the current object. (Inherited from Object.) |
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Validate | Determines whether the specified object is valid and throws a ValidationException if the object is not valid. (Inherited from ValidationAttribute.) |
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Remarks
You apply the RequiredAttribute attribute to a property to specify that the property must contain a value. A validation exception is raised if the property is nulla null reference (Nothing in Visual Basic), an empty string (""), or contains only white-space characters.
Examples
The following example shows how to apply the RequiredAttribute attribute to a property that contains values for a last name.
Public Class Customer
<Required()> _
<StringLength(50)> _
Public Property LastName As String
'Implement Get and Set logic
End Property
End Class
public class Customer
{
[Required]
[StringLength(50)]
public string LastName { get; set; }
}
Version Information
Silverlight
Supported in: 5, 4, 3
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
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.
See Also