Modifying HTML attributes passed to custom HtmlHelper extensions

Question

I'm trying create a custom HTML helper extension method that takes an object htmlAttributes and then get the passed in values (via reflection) and add to them into a Dictionary<string, object>. Unfortunately, this does not work although there is an overload in the InputExtensions class that takes a Dictionary<string, object> htmlAttributes as a parameter.

The problem is that this dictionary is not being processed properly somewhere inside the razor engine (I guess...). Here's how it is being output as HTML:

<input name="FirstName" id="FirstName" type="text" Values="System.Collections.Generic.Dictionary`2+ValueCollection[System.String,System.Object]" Keys="System.Collections.Generic.Dictionary`2+KeyCollection[System.String,System.Object]" Count="3" Comparer="System.Collections.Generic.GenericEqualityComparer`1[System.String]"/>

And here's my code:

    Dictionary<String, Object> attributes = new Dictionary<String, Object>();
    attributes.Add("readonly", "readonly");
    PropertyInfo[] properties = htmlAttributes.GetType().GetProperties();
    foreach (PropertyInfo propertyInfo in properties)
    {                                        
        if (propertyInfo.Name.Equals("class"))
        {
            attributes.Add("class", String.Format("{0} {1}", "readOnly", propertyInfo.GetValue(htmlAttributes, null)));
        }
        else
        {
            attributes.Add(propertyInfo.Name, propertyInfo.GetValue(htmlAttributes, null));
        }
    }

    genericMethod = methodInfo.MakeGenericMethod(new[] { typeof(TModel), typeof(TProperty) });
    result = genericMethod.Invoke(null, new object[] { helper, expression, (Dictionary<String, Object>)attributes }) as MvcHtmlString;

P.S: This is a follow up to this question.

Buildstarted · Accepted Answer · 2012-05-17 15:28:07Z

2

You should be able to call the TextBoxFor method directly and pass in the expression and your new html attributes.

public static IHtmlString Test<TModel, TProperty>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes)
{
    Dictionary<String, Object> attributes = new Dictionary<String, Object>();
    attributes.Add("readonly", "readonly");
    PropertyInfo[] properties = htmlAttributes.GetType().GetProperties();
    foreach (PropertyInfo propertyInfo in properties)
    {
        if (propertyInfo.Name.Equals("class"))
        {
            attributes.Add("class", String.Format("{0} {1}", "readOnly", propertyInfo.GetValue(htmlAttributes, null)));
        }
        else
        {
            attributes.Add(propertyInfo.Name, propertyInfo.GetValue(htmlAttributes, null));
        }
    }

    //call the input tag
    return helper.TextBoxFor(expression, htmlAttributes);
}

edited May 17, 2012 at 15:28

answered May 17, 2012 at 14:59

Buildstarted

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4 Comments

jrummell Over a year ago

There's a RouteValueDictionary constructor overload that accepts object as well. No need to use reflection.

Buildstarted Over a year ago

The overload for that just does the same thing but you're right that you can use that easier.

Kassem Over a year ago

I tried to create an instance of RouteValueDictionary that takes the attributes dictionary, and then pass that instance as the parameter of the invoked method, but still that did not change anything! All I need to do is be able to modify the htmlAttributes object, so if I could get rid of the dictionary altogether that would be perfect.

Buildstarted Over a year ago

Ok, I see your problem. What are you trying to return from your extension? Just the string of html attributes or the entire tag itself?

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