How to check if a file exists in a folder?

Use FileInfo.Exists Property:

DirectoryInfo di = new DirectoryInfo(ProcessingDirectory);
FileInfo[] TXTFiles = di.GetFiles("*.xml");
if (TXTFiles.Length == 0)
{
    log.Info("no files present")
}
foreach (var fi in TXTFiles)
    log.Info(fi.Exists);

or File.Exists Method:

string curFile = @"c:\temp\test.txt";
Console.WriteLine(File.Exists(curFile) ? "File exists." : "File does not exist.");

To check file exists or not you can use

System.IO.File.Exists(path)

This is a way to see if any XML-files exists in that folder, yes.

To check for specific files use File.Exists(path), which will return a boolean indicating wheter the file at path exists.

Since nobody said how to check if the file exists AND get the current folder the executable is in (Working Directory):

if (File.Exists(Directory.GetCurrentDirectory() + @"\YourFile.txt")) {
                //do stuff
}

The @"\YourFile.txt" is not case sensitive, that means stuff like @"\YoUrFiLe.txt" and @"\YourFile.TXT" or @"\yOuRfILE.tXt" is interpreted the same.