im making file upload  user control.
one of the control properties is the allowed formats:
myUpload.allowedFormats = "gif|jpg|doc|txt|ppt|xls|htm|html";

now,i took the file  name and split the name and compare this string (split it
also) to the file extension.

it is not a good approch since a person can rename the file name to something
like:

myFile.jpg.exe

...

so what is the solution?if im taking myFile.postedFile.contentType

im getting in word application upload : application\msword...

i need the extension to compare to what the developer put in the property
(doc,htm...)

This probably isn't the greatest solution, but you could determine your file
extentions in the following way:

string allowedFormats = "|gif|jpg|doc|txt|ppt|xls|htm|html|";
string x = "file.jpg";
Response.Write(x.Split(new char[] {'.'}, 2)[1] + "<br>");
if (allowedFormats.IndexOf("|" + x.Split(new char[] {'.'}, 2)[1] + "|") >
0 )
{
Response.Write("this extension is ok<br>");
}
else
{
Response.Write("this extension is NOT ok<br>");
}

string y = "file.jpg.ext";
Response.Write(y.Split(new char[] {'.'}, 2)[1] + "<br>");
if (allowedFormats.IndexOf("|" + y.Split(new char[] {'.'}, 2)[1] + "|") >
0 )
{
Response.Write("this extension is ok<br>");
}
else
{
Response.Write("this extension is NOT ok<br>");
}

How about System.IO.Path.GetExtension() ?

look up the whole System.IO.Path "tree" on MSDN, you'll find lots of
goodies that should help in building an uploader.