Html helper for <input type=“file” />

Question

Is there a HTMLHelper for file upload? Specifically, I am looking for a replace of

<input type="file"/>

using ASP.NET MVC HTMLHelper.

Or, If I use

using (Html.BeginForm()) 

What is the HTML control for the file upload?

Answer 1

HTML Upload File ASP MVC 3.

Model: (Note that FileExtensionsAttribute is available in MvcFutures. It will validate file extensions client side and server side.)

public class ViewModel
{
    [Required, Microsoft.Web.Mvc.FileExtensions(Extensions = "csv", 
             ErrorMessage = "Specify a CSV file. (Comma-separated values)")]
    public HttpPostedFileBase File { get; set; }
}

HTML View:

@using (Html.BeginForm("Action", "Controller", FormMethod.Post, new 
                                       { enctype = "multipart/form-data" }))
{
    @Html.TextBoxFor(m => m.File, new { type = "file" })
    @Html.ValidationMessageFor(m => m.File)
}

Controller action:

[HttpPost]
public ActionResult Action(ViewModel model)
{
    if (ModelState.IsValid)
    {
        // Use your file here
        using (MemoryStream memoryStream = new MemoryStream())
        {
            model.File.InputStream.CopyTo(memoryStream);
        }
    }
}

Answer 2

Or you could do it properly:

In your HtmlHelper Extension class:

public static MvcHtmlString FileFor<TModel, TProperty>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression)
    {
        return helper.FileFor(expression, null);
    }

public static MvcHtmlString FileFor<TModel, TProperty>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes)
    {
        var builder = new TagBuilder("input");

        var id = helper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(ExpressionHelper.GetExpressionText(expression));
        builder.GenerateId(id);
        builder.MergeAttribute("name", id);
        builder.MergeAttribute("type", "file");

        builder.MergeAttributes(new RouteValueDictionary(htmlAttributes));

        // Render tag
        return MvcHtmlString.Create(builder.ToString(TagRenderMode.SelfClosing));
    }

This line:

var id = helper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(ExpressionHelper.GetExpressionText(expression));

Generates an id unique to the model, you know in lists and stuff. model[0].Name etc.

Create the correct property in the model:

public HttpPostedFileBase NewFile { get; set; }

Then you need to make sure your form will send files:

@using (Html.BeginForm("Action", "Controller", FormMethod.Post, new { enctype = "multipart/form-data" }))

Then here's your helper:

@Html.FileFor(x => x.NewFile)