Good way to check if file extension is of an image or not

Question

I have this file types Filters:

    public const string Png = "PNG Portable Network Graphics (*.png)|" + "*.png";     public const string Jpg = "JPEG File Interchange Format (*.jpg *.jpeg *jfif)|" + "*.jpg;*.jpeg;*.jfif";     public const string Bmp = "BMP Windows Bitmap (*.bmp)|" + "*.bmp";     public const string Tif = "TIF Tagged Imaged File Format (*.tif *.tiff)|" + "*.tif;*.tiff";     public const string Gif = "GIF Graphics Interchange Format (*.gif)|" + "*.gif";     public const string AllImages = "Image file|" + "*.png; *.jpg; *.jpeg; *.jfif; *.bmp;*.tif; *.tiff; *.gif";     public const string AllFiles = "All files (*.*)" + "|*.*";      static FilesFilters()     {         imagesTypes = new List<string>();         imagesTypes.Add(Png);         imagesTypes.Add(Jpg);         imagesTypes.Add(Bmp);         imagesTypes.Add(Tif);         imagesTypes.Add(Gif);    } 

OBS: Is there any default filters in .NET or a free library for that?

I need a static method that checks if a string is an image or not. How would you solve this?

    //ext == Path.GetExtension(yourpath)     public static bool IsImageExtension(string ext)     {         return (ext == ".bmp" || .... etc etc...)     } 

Solution using Jeroen Vannevel EndsWith. I think it is ok.

    public static bool IsImageExtension(string ext)     {         return imagesTypes.Contains(ext);     } 

Answer 1

You could use .endsWith(ext). It's not a very secure method though: I could rename 'bla.jpg' to 'bla.png' and it would still be a jpg file.

public static bool HasImageExtension(this string source){  return (source.EndsWith(".png") || source.EndsWith(".jpg")); } 

This provides a more secure solution:

string InputSource = "mypic.png"; System.Drawing.Image imgInput = System.Drawing.Image.FromFile(InputSource); Graphics gInput = Graphics.fromimage(imgInput); Imaging.ImageFormat thisFormat = imgInput.rawformat; 

Answer 2

private static readonly string[] _validExtensions = {"jpg","bmp","gif","png"}; //  etc  public static bool IsImageExtension(string ext) {     return _validExtensions.Contains(ext.ToLower()); } 

If you want to be able to make the list configurable at runtime without recompiling, add something like:

private static string[] _validExtensions;  private static string[] ValidExtensions() {     if(_validExtensions==null)     {          // load from app.config, text file, DB, wherever     }     return _validExtensions }  public static bool IsImageExtension(string ext) {     return ValidExtensions().Contains(ext.ToLower()); }