Custom Data Annotations ASP.NET MVC C#

Question

I have the follwing question about MVC 2 with C#.

Here is my Model:

public class Pmjob
{
   [Tooltext="Hier soll der Name eingegeben werden"]
   [DisplayName("Type")]
   public int Name { get; set; }
}

Now I want to reach the Tooltext item in my view, e. g.:

@Html.ToolTextFor(Model => Model.Pmjob.Name)

or in the BL:

if ( Model.Pmjob.Name.Tooltext == "") {
}

Is this possible?

Answer 1

Create an abstract class MetaDataAttribute :

public abstract class MetadataAttribute : Attribute
{
    /// <summary>
    /// Method for processing custom attribute data.
    /// </summary>
    /// <param name="modelMetaData">A ModelMetaData instance.</param>
    public abstract void Process(ModelMetadata modelMetaData);
}

Make your attribute inherit from MetaDataAttribute :

public class ToolTextAttribute : MetadataAttribute
{
    public string Text { get; set; }
    public TooltextAttribute(string text)
    {
        this.Text = new text;
    }

    public override void Process(ModelMetadata modelMetaData)
    {
        modelMetaData.AdditionalValues.Add("ToolText", this.Text);
    }
}

Create the custom MetaDataProvider :

public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    protected override ModelMetadata CreateMetadata(
        IEnumerable<Attribute> attributes,
        Type containerType,
        Func<object> modelAccessor,
        Type modelType,
        string propertyName)
    {
        var modelMetadata = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);
        attributes.OfType<MetadataAttribute>().ToList().ForEach(x => x.Process(modelMetadata));
        return modelMetadata;
    }
}

And replace the default one (global.asax.cs) :

protected void Application_Start()
{
    // snipped

    ModelMetadataProviders.Current = new CustomModelMetadataProvider();
}

Finally, you can access it in your view (or in a Html Helper ) :

(string)ViewData.ModelMetadata.AdditionalValues.Where(x => x.Key == "ToolText").SingleOrDefault()

Source :

• http://weblogs.asp.net/seanmcalinden/archive/2010/06/11/custom-asp-net-mvc-2-modelmetadataprovider-for-using-custom-view-model-attributes.aspx
• http://weblogs.asp.net/seanmcalinden/archive/2010/06/12/asp-net-mvc-2-auto-complete-textbox-custom-view-model-attribute-amp-editortemplate.aspx