C# Check File Extension In Array Of Valid Extension

Posted by Hoan Huynh in CSharp

December 4, 2011

1 Comment

Assume that we’re building an upload function that allow people be able to upload either photo or video to server. Before storing the uploaded file to hard drive of web server, we need to verify that file extension is valid. And file extension validation is the first and important step in the checking process.

This post provides a simple function (with 2 input parameters: extension and type string) that validate file extension for video and photo. And each part will have an array of accepted extensions.

C# Check File Extension

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
 
public partial class check_valid_extension : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        int is_valid = 0;
 
        is_valid = chkValidExtension(".jpg", "photo");
 
        if (is_valid == 1)
        {
            Response.Write("The file extension is valid");
        }
        else if (is_valid == 0)
        {
            Response.Write("The file extension is not valid");
        }
    }
 
    public int chkValidExtension(string ext, string type)
    {
        if (type == "photo")
        {
            string[] PosterAllowedExtensions = new string[] { ".gif", ".jpeg", ".jpg", ".png" };
            for (int i = 0; i < PosterAllowedExtensions.Length; i++)
            {
                if (ext == PosterAllowedExtensions[i])
                    return 1;
            }
 
            return 0;
        }
        else if (type == "video")
        {
            string[] TrailerAllowedExtensions = new string[] { ".flv", ".asf", ".avi", ".wmv", ".mp4", ".mov", ".3gp", ".m4v", ".3g2" };
            for (int i = 0; i < TrailerAllowedExtensions.Length; i++)
            {
                if (ext == TrailerAllowedExtensions[i])
                    return 1;
            }
 
            return 0;
        }
 
        return 0;
    }
}

First you need to get file extension from the uploaded file and pass it to chkValidExtension function as “ext” parameter and pass “video” or “photo” for “type” parameter depend on your need.

Tagged: Array Extension