Restricting File upload box type

<!-- Match all image files (image/*) -->
<input type="file" accept="image/*">

<!-- Match all video files (video/*) -->
<input type="file" accept="video/*">

<!-- Match all audio files (audio/*) -->
<input type="file" accept="audio/*">

<!-- Match all image files (image/*) and files with the extension ".someext" -->
<input type="file" accept=".someext,image/*">
<!-- See note below -->

<!-- Match all image files (image/*) and video files (video/*) -->
<input type="file" accept="image/*,video/*">
<!-- See note below -->

The accept attribute may be specified to provide user agents with a hint of what file types will be accepted.

If specified, the attribute must consist of a set of comma-separated tokens, each of which must be anASCII case-insensitive match for one of the following:

The string audio/*

Indicates that sound files are accepted.


The string video/*

Indicates that video files are accepted.


The string image/*

Indicates that image files are accepted.


A valid MIME type with no parameters

Indicates that files of the specified type are accepted.


A string whose first character is a U+002E FULL STOP character (.)

Indicates that files with the specified file extension are accepted.


Source (HTML Specification)

Hashing

using System.Security.Cryptography;
private string GetHash(string text, string passwordFormat)
    {
        HashAlgorithm _algorithm;
        switch (passwordFormat.ToUpper())
        {
            case "MD5":
                _algorithm = MD5.Create();
                break;
            case "SHA1":
                _algorithm = SHA1.Create();
                break;
            case "SHA256":
                _algorithm = SHA256.Create();
                break;
            case "SHA512":
                _algorithm = SHA512.Create();
                break;
            default:
                throw new ArgumentException("Invalid password format.", "passwordFormat");
        }
        byte[] bytes = Encoding.UTF8.GetBytes(text);
        byte[] hash = _algorithm.ComputeHash(bytes);
        string hashString = string.Empty;
        foreach (byte x in hash)
        {
            hashString += String.Format("{0:x2}", x);
        }
        return hashString.ToLowerInvariant();
    }