YaldaValidation For FileUpload Control

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Introduction

Validate the Extionsions that you need and the size of the upload file with YaldaValidation!!!

This validation control named "YaldaValidation" is a custom validation control that gets the job easily for those working with file upload. It is quiet simple and easy to use.

How to use 

Just add the C# class to your App_Code folder. Look at this code snippet:

<%@ Register TagPrefix="custom" Namespace="testproject.App_Code" Assembly="App_Code" %>

You have to register this custom validator (if you just paste this below code it will ask you to generate automatically the register declare).

the YaldaValidation

<custom:YaldaValidator ControlToValidate="FileUpload1" 
    Display="Dynamic" Extensions="jpeg+png" runat="server"
    SizeOfTheFileInKb="100" ErrorMessage="*"> 
</custom:YaldaValidator>

This validation has the same attributes of base validation, but there are two more attributes that make it useful for me!

First is Extensions: you put your extensions here and leave a + between the extension names!

Second is SizeOfTheFileInKb: you set the file size in KB and if the uploaded file is bigger than that, the validator causes a validation error!

How It Works

I create a new validation control by deriving a new control from the BaseValidator class. This is the base class for all validation controls.

basevalidator is a MustInherit (abstract) class, which requires to implement a single method: EvaluateIsValid => Returns true when the form field being validated is valid.

You just need to override this method.

My YaldaValidator.cs class code

using System.Linq;
using System.Web.UI.WebControls;
namespace testproject.App_Code
{ 
    /// <summary>
    /// validate the file extension, size, and exists of a file in FileUpload Control
    /// </summary>
    public class YaldaValidator : BaseValidator
    {
        string _extensions = "";
        public string Extensions
        {
            get { return _extensions; }
            set { _extensions = value; }
        }
 
        int _sizeOfTheFileInKb = 1;
        public int SizeOfTheFileInKb
        {
            get { return _sizeOfTheFileInKb; }
            set { _sizeOfTheFileInKb = value; }
        }
        protected override bool EvaluateIsValid()
        {
            FileUpload fu = (FileUpload)FindControl(this.ControlToValidate);            
            string[] ex = _extensions.Split('+');
            if (fu.HasFile && fu.PostedFile.ContentLength <= _sizeOfTheFileInKb * 
                1024 && ex.Contains(System.IO.Path.GetExtension(fu.PostedFile.FileName).Substring(1)))
            { 
                return true; 
            } 
            else 
            {
                return false; 
            } 
        } 
    } 
}

Code Explanation

I get the extensions as a string set it to _Extensions. And I get the file size as int in kb an set to _SizeOfTheFileInKb. In the EvaluateIsValid() method I find the FileUpload control (get ID by this.ControlToValidate).

FileUpload fu = (FileUpload)FindControl(this.ControlToValidate);

Then make the string into a array of strings using the .Split() method.

string[] ex = _extensions.Split('+');

In the if clause, I check if the file exists using the .HasFile() method, and then compare the size of the existing file with the valid size (it's a multiple of 1024 because it's in KB).

At last check the file extension with one of the given extension names.

if (fu.HasFile && fu.PostedFile.ContentLength <= _sizeOfTheFileInKb * 1024 && 
     ex.Contains(System.IO.Path.GetExtension(fu.PostedFile.FileName).Substring(1)))

If the conditions return true, you can upload your file.