DataTypeAttribute Class

Definition

Namespace:

System.ComponentModel.DataAnnotations

Assembly:

System.ComponentModel.Annotations.dll

Source:

DataTypeAttribute.cs

Specifies the name of an additional type to associate with a data field.

public ref class DataTypeAttribute : System::ComponentModel::DataAnnotations::ValidationAttribute

[System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Method | System.AttributeTargets.Parameter | System.AttributeTargets.Property, AllowMultiple=false)]
public class DataTypeAttribute : System.ComponentModel.DataAnnotations.ValidationAttribute

[<System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Method | System.AttributeTargets.Parameter | System.AttributeTargets.Property, AllowMultiple=false)>]
type DataTypeAttribute = class
    inherit ValidationAttribute

Public Class DataTypeAttribute
Inherits ValidationAttribute

Inheritance

Object

Attribute

ValidationAttribute

DataTypeAttribute

Derived

System.ComponentModel.DataAnnotations.CreditCardAttribute

System.ComponentModel.DataAnnotations.EmailAddressAttribute

System.ComponentModel.DataAnnotations.EnumDataTypeAttribute

System.ComponentModel.DataAnnotations.FileExtensionsAttribute

System.ComponentModel.DataAnnotations.PhoneAttribute

System.ComponentModel.DataAnnotations.UrlAttribute

Attributes

AttributeUsageAttribute

Examples

The following example uses the DataTypeAttribute attribute to customize the display of the EmailAddress data field. The email addresses are shown as hyperlinks instead of as simple text, which is what Dynamic Data would infer from the intrinsic data type. The example code is in three parts, and it performs the following steps:

• It implements a metadata partial class and the associated metadata class.

• In the associated metadata class, it applies the DataTypeAttribute attribute to the EmailAddress data field by specifying the EmailAddress enumerated value. This indicates to the Text.ascx field template that it should customize the display of email addresses.

• It modifies the Text.ascx field template to customize the display of the EmailAddress data fields.

using System;
using System.Web.DynamicData;
using System.ComponentModel.DataAnnotations;

[MetadataType(typeof(CustomerMetaData))]
public partial class Customer
{
}

public class CustomerMetaData
{

    // Add type information.
    [DataType(DataType.EmailAddress)]
    public object EmailAddress;
}

Imports System.Web.DynamicData
Imports System.ComponentModel.DataAnnotations

<MetadataType(GetType(CustomerMetadata))> _
Partial Public Class Customer


End Class

Public Class CustomerMetadata

    ' Add type information.
    <DataType(DataType.EmailAddress)> _
    Public EmailAddress As Object

End Class

<%@ Control Language="C#" 
CodeFile="Text.ascx.cs" Inherits="TextField" %>

<!-- Removed, evaluated in the code behind.
<%# FieldValueString %> -->

<%@ Control Language="VB" 
  CodeFile="Text.ascx.vb" Inherits="TextField" %>

<!-- Removed, evaluated in the code behind.
<%# FieldValueString %> -->

using System;
using System.Linq;
using System.Web.UI.WebControls;
using System.Web.DynamicData;
using System.ComponentModel.DataAnnotations;

public partial class TextField : 
    System.Web.DynamicData.FieldTemplateUserControl {

    protected override void OnDataBinding(EventArgs e)
    {
        base.OnDataBinding(e);
        bool processed = false;
        var metadata = MetadataAttributes.OfType
            <DataTypeAttribute>().FirstOrDefault();
        if (metadata != null)
        {
            if (metadata.DataType == DataType.EmailAddress)
            {
                if (!string.IsNullOrEmpty(FieldValueString))
                {
                    processed = true;
                    HyperLink hyperlink = new HyperLink();
                    hyperlink.Text = FieldValueString;
                    hyperlink.NavigateUrl = "mailto:" + FieldValueString;
                    Controls.Add(hyperlink);
                }
            }
        }
        if (!processed)
        {
            Literal literal = new Literal();
            literal.Text = FieldValueString;
            Controls.Add(literal);
        }
    }
}

Imports System.Linq
Imports System.Web.UI.WebControls
Imports System.Web.DynamicData
Imports System.ComponentModel.DataAnnotations

Partial Public Class TextField
    Inherits System.Web.DynamicData.FieldTemplateUserControl

    Protected Overloads Overrides Sub OnDataBinding(ByVal e As EventArgs)
        MyBase.OnDataBinding(e)
        Dim processed As Boolean = False
        Dim metadata As DataTypeAttribute = _
           MetadataAttributes.OfType(Of DataTypeAttribute)().FirstOrDefault()
        If metadata IsNot Nothing Then
            If metadata.DataType = DataType.EmailAddress Then
                If Not String.IsNullOrEmpty(FieldValueString) Then
                    processed = True
                    Dim hyperlink As New HyperLink()
                    hyperlink.Text = FieldValueString
                    hyperlink.NavigateUrl = "mailto:" + FieldValueString
                    Controls.Add(hyperlink)
                End If
            End If
        End If
        If Not processed Then
            Dim literal As New Literal()
            literal.Text = FieldValueString
            Controls.Add(literal)
        End If
    End Sub

End Class

To compile and run the example code, you need the following:

• Any edition of Visual Studio 2010 or later.

• The AdventureWorksLT sample database. For information about how to download and install the SQL Server sample database, see Microsoft SQL Server Product Samples: Database on GitHub. Make sure that you install the correct version of the sample database for the version of SQL Server that you are running.

• A data-driven Web site. This enables you to create a data context for the database and to create the class that contains the data field to customize. For more information, see Walkthrough: Creating a New Dynamic Data Web Site using Scaffolding.

Remarks

The DataTypeAttribute attribute enables you to mark fields by using a type that is more specific than the database intrinsic type. The type name is selected from the DataType enumeration type. For example, a string data field that contains email addresses can be specified as the EmailAddress type. This information is then accessed by the field templates to modify how the data field is processed.

You use the DataTypeAttribute attribute for the following reasons:

• To provide additional type information for a data field. You do this by applying the DataTypeAttribute attribute to a data field in the data model and by specifying the additional type name from the DataType enumeration. The field template that processes the data field can access this additional metadata type information to determine how to process the field. For example, the text field template can generate hyperlinks for email addresses whose intrinsic type is String.

• To associate a custom field template with a data field. The specified custom field template will then be used to process the data field. This is an alternative to using the UIHintAttribute attribute.

When you apply the DataTypeAttribute attribute to a data field you must do the following:

• Follow the attribute usage rules.

• Implement the metadata class that contains the data fields to which you want to apply the attribute.

• Issue validation errors as appropriate.

For more information, see ASP.NET Dynamic Data Guidelines.

Constructors

DataTypeAttribute(DataType)	Initializes a new instance of the DataTypeAttribute class by using the specified type name.
DataTypeAttribute(String)	Initializes a new instance of the DataTypeAttribute class by using the specified field template name.

Properties

CustomDataType	Gets the name of custom field template that is associated with the data field.
DataType	Gets the type that is associated with the data field.
DisplayFormat	Gets a data-field display format.
ErrorMessage	Gets or sets an error message to associate with a validation control if validation fails. (Inherited from ValidationAttribute)
ErrorMessageResourceName	Gets or sets the error message resource name to use in order to look up the ErrorMessageResourceType property value if validation fails. (Inherited from ValidationAttribute)
ErrorMessageResourceType	Gets or sets the resource type to use for error-message lookup if validation fails. (Inherited from ValidationAttribute)
ErrorMessageString	Gets the localized validation error message. (Inherited from ValidationAttribute)
RequiresValidationContext	Gets a value that indicates whether the attribute requires validation context. (Inherited from ValidationAttribute)
TypeId	When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute)

Methods

Equals(Object)	Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute)
FormatErrorMessage(String)	Applies formatting to an error message, based on the data field where the error occurred. (Inherited from ValidationAttribute)
GetDataTypeName()	Returns the name of the type that is associated with the data field.
GetHashCode()	Returns the hash code for this instance. (Inherited from Attribute)
GetType()	Gets the Type of the current instance. (Inherited from Object)
GetValidationResult(Object, ValidationContext)	Checks whether the specified value is valid with respect to the current validation attribute. (Inherited from ValidationAttribute)
IsDefaultAttribute()	When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute)
IsValid(Object)	Checks that the value of the data field is valid.
IsValid(Object, ValidationContext)	Validates the specified value with respect to the current validation attribute. (Inherited from ValidationAttribute)
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)
Validate(Object, String)	Validates the specified object. (Inherited from ValidationAttribute)
Validate(Object, ValidationContext)	Validates the specified object. (Inherited from ValidationAttribute)

See also

• ValidationAttribute
• UIHintAttribute
• DataType
• AttributeUsageAttribute
• AttributeTargets
• How to: Customize Data Field Appearance and Behavior For Non-Intrinsic Data Types in the Data Model
• Extending Metadata Using Attributes