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RequiredAttribute Class

Specifies that a value must be provided for a property.

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)

[AttributeUsageAttribute(AttributeTargets.Property|AttributeTargets.Field|AttributeTargets.Parameter, AllowMultiple = false)]
public class RequiredAttribute : ValidationAttribute

The RequiredAttribute type exposes the following members.

  NameDescription
Public methodRequiredAttributeInitializes a new instance of the RequiredAttribute class.
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  NameDescription
Public propertyAllowEmptyStringsGets or sets a value that indicates whether an empty string is allowed.
Public propertyErrorMessageGets or sets the non-localizable error message to display when validation fails. (Inherited from ValidationAttribute.)
Public propertyErrorMessageResourceNameGets or sets the property name on the resource type that provides the localizable error message. (Inherited from ValidationAttribute.)
Public propertyErrorMessageResourceTypeGets or sets the resource type that provides the localizable error message. (Inherited from ValidationAttribute.)
Protected propertyErrorMessageStringGets the localized or non-localized error message. (Inherited from ValidationAttribute.)
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  NameDescription
Public methodEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodFormatErrorMessageApplies formatting to the error message. (Inherited from ValidationAttribute.)
Public methodGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodGetValidationResultDetermines whether the specified object is valid and returns an object that includes the results of the validation check. (Inherited from ValidationAttribute.)
Protected methodIsValidDetermines whether the specified object is valid. (Inherited from ValidationAttribute.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodValidateDetermines whether the specified object is valid and throws a ValidationException if the object is not valid. (Inherited from ValidationAttribute.)
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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 null, an empty string (""), or contains only white-space characters.

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 string LastName { get; set; }
}


Silverlight

Supported in: 5, 4, 3

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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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