Question

I have a text box created using

@Html.TextBoxFor(m => m.Model1.field1, new { @class = "login-input", @name="Name",  @Value = "test" })

I want to change the default value of this textbox from “text” to a value stored in a model field. How do i set a model field as the the value attribute? Say the Name of the model to be called is Model2 and the attribute is field2. How do I set the value of the textbox to field2?

Answer 1

You must first write an Extension Method like this:

public class ObjectExtensions
{
    public static string Item<TItem, TMember>(this TItem obj, Expression<Func<TItem, TMember>> expression)
    {
        if (expression.Body is MemberExpression)
        {
            return ((MemberExpression)(expression.Body)).Member.Name;
        }
        if (expression.Body is UnaryExpression)
        {
            return ((MemberExpression)((UnaryExpression)(expression.Body)).Operand).Member.Name;
        }
        if (expression.Body is ParameterExpression)
        {
            return expression.Body.Type.Name;
        }
        throw new InvalidOperationException();
    }
 }

It will extract the Name of property when you write sth like this: @Html.TextBoxFor(m => m.Model1.field1)

then you can use it like this:

Html.TextBoxFor(m => m.Model1.field1, 
  new { @class = "login-input", 
        @name="Name",  
        @value = Model.Item(m => m.Model1.field1) })

If you don’t want to call m => m.Model1.field1 again, you must declare your version of TextBoxFor method which is more complicate, but If you want I can provide you the details.

This is a sample from my code base on Github:

public static class HtmlHelperExtensionForEditorForDateTime
{

    public static MvcHtmlString Editor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression)
    {
        ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);


        string propname = html.ViewData.Model.Item(expression);
        string incomingValue = null;
        var httpCookie = html.ViewContext.RequestContext.HttpContext.Request.Cookies["lang"];
        if (metadata.Model is DateTime && (httpCookie.IsNull() || httpCookie.Value == Cultures.Persian))
            incomingValue = PersianCalendarUtility.ConvertToPersian(((DateTime)metadata.Model).ToShortDateString());
        if (string.IsNullOrEmpty(incomingValue))
            return html.TextBox(propname, null, new { @class = "datepicker TextField" });

        return html.TextBox(propname, incomingValue, new { @class = "datepicker TextField"});
    }

}