Question

I’ve been following this guide on creating custom display attributes (specifically extra html attributes) to apply to the properties in my ViewModel. I have overridden both String and Boolean in the EditorTemplates folder. The editor template checks to see if a value has been set/the display attribute has been used – and adds the additional html attributes.

I’m getting stuck on the Boolean override when performing an edit action though. Regardless of whether or not I apply the attribute to a string, the ViewModel always maps with the correct existing data. This isn’t true with any other form input type, due to the way the templates have been written by changing the type attribute inside a TextBoxFor.

I’ve been writing this primarily because I have been digging into knockout, and wanted an easy way to apply the data-bind attribute to strongly-typed views – if there’s a better way please let me know!

Attribute Code:

    public class Knockout : Attribute 
{
    public string DataBind { get; set; }
    public string InputType { get; set; }

    /*
    Example:
    Knockout("checked: showUploader", "checkbox")      
    Adds the HTML attributes data-bind="checked: showUploader" type="checkbox"
    */
    public Knockout(string dataBind, string inputType)
    {
        this.DataBind = dataBind;
        this.InputType = inputType;
    }
    public Dictionary<string, object> OptionalAttributes()
    {
        var options = new Dictionary<string, object>();

        if(!string.IsNullOrWhiteSpace(DataBind))
        {
            options.Add("data-bind", DataBind);
        }

        if (!string.IsNullOrWhiteSpace(InputType))
        {
            options.Add("type", InputType);
        }
        return options;
    }
}

Template Code

@using CumbriaMD.Infrastructure.ViewModels.DisplayAttributes
@{
   var key = "Knockout";
}

@if (ViewData.ModelMetadata.AdditionalValues.ContainsKey(key))
{
   var knockout = ViewData.ModelMetadata.AdditionalValues[key] as Knockout;
   @Html.TextBoxFor(model => model, knockout.OptionalAttributes())
}
else
{

/*
When the attribute is not present, the default action is the following - which seems to
be overriding the data mapped from the database:
*/
    @Html.TextBoxFor(model => model, new { type="checkbox" })
}

Answer 1

Found the answer nested in this beauty of a question!

My working template for boolean values now looks like:

@using CumbriaMD.Infrastructure.ViewModels.DisplayAttributes
@{
   var key = "Knockout";
   bool? value = null;
   if(ViewData.Model != null)
   {
      value = Convert.ToBoolean(ViewData.Model, System.Globalization.CultureInfo.InvariantCulture);
   }
}

@if (ViewData.ModelMetadata.AdditionalValues.ContainsKey(key))
{
   var knockout = ViewData.ModelMetadata.AdditionalValues[key] as Knockout;
   @Html.CheckBox("", value ?? false, knockout.OptionalAttributes())
}
else
{
   @Html.CheckBox("", value ?? false, new { @class = "check-box" })
}