How do the MVC html helpers use expressions to get an objects property

Question

For example:

Html.TextBoxFor(x => x.ModelProperty)

If I were to get an expression like this as a method argument, how would I get the referenced property from the expression? My experience with expressions is somewhat limited and based on what I know, I don't get how this works.

Answer 1

You can get property name easily like this:

var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
var propName = metadata.PropertyName;

Or you can get property and its attributes:

MemberExpression memberExpression = (MemberExpression) expression.Body;
var member = memberExpression.Member as PropertyInfo;
var attributes = member.GetCustomAttributes();

For example you can write a simple method that generates a input element like this:

public static MvcHtmlString TextboxForCustom<TModel, TResult>(this HtmlHelper<TModel> html,
        Expression<Func<TModel, TResult>> expression)
    {
        var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
        var propName = metadata.PropertyName;

        StringBuilder sb = new StringBuilder();
        sb.AppendFormat("<input type=\"text\" id=\"{0}\" />", propName);

        return MvcHtmlString.Create(sb.ToString());

    }

Take a look at my answer here.