C# – foreach on Request.Files

asp.netcfile upload

I'm attempting upload multiple files in ASP.NET MVC and I have this simple foreach loop in my controller

foreach (HttpPostedFileBase f in Request.Files)
{
    if (f.ContentLength > 0)
        FileUpload(f);
}

The previous code generates this error:

Unable to cast object of type 'System.String' to type 'System.Web.HttpPostedFile'.

What I don't understand is why Request.Files[1] returns an HttpPostedFileBase but when it's iterated over, it returns strings (presumably the file names).

Note: I know this can be solved with a for loop.
Also, I tried using HttpPostedFile, with the same error.

Best Answer

The enumerator on the HttpFileCollection returns the keys (names) of the files, not the HttpPostedFileBase objects. Once you get the key, use the Item ([]) property with the key (filename) to get the HttpPostedFileBase object.

foreach (string fileName in Request.Files)
{
    HttpPostedFileBase file = Request.Files[fileName];

    ...
}

Related Solutions

C# – How to get the index of the current iteration of a foreach loop

Ian Mercer posted a similar solution as this on Phil Haack's blog:

foreach (var item in Model.Select((value, i) => new { i, value }))
{
    var value = item.value;
    var index = item.i;
}

This gets you the item (item.value) and its index (item.i) by using this overload of LINQ's Select:

the second parameter of the function [inside Select] represents the index of the source element.

The new { i, value } is creating a new anonymous object.

Heap allocations can be avoided by using ValueTuple if you're using C# 7.0 or later:

foreach (var item in Model.Select((value, i) => ( value, i )))
{
    var value = item.value;
    var index = item.i;
}

You can also eliminate the item. by using automatic destructuring:

<ol>
foreach ((MyType value, Int32 i) in Model.Select((value, i) => ( value, i )))
{
    <li id="item_@i">@value</li>
}
</ol>

C# – Invalid Cast Exception in HttpFileCollection

If you look at the code sample on this page, it shows how you should enumerate the collection, you are in fact getting a string when you try to enumerate as you are.

http://msdn.microsoft.com/en-us/library/system.web.httpfilecollection.aspx

Best Answer

Related Solutions

C# – How to get the index of the current iteration of a foreach loop

C# – Invalid Cast Exception in HttpFileCollection

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