Question

I have a C# winform application that is outputting to excel files.
Let’s say the name format of the file name is: Output1.xlsl

I would like to have the output saved to another sequential file on each button click/execution.
So next it would be Output2.xlsl, Output3.xlsl… etc.

How to check that, I know of checking if the file exists, but how to check for the numbering?

FileInfo newExcelFile = new FileInfo(@"Output1.xlsx");
if (newExcelFile.Exists)
{
      ...
}

Answer 1

You could use this loop and File.Exists with Path.Combine:

string directory = @"C:\SomeDirectory";
string fileName = @"Output{0}.xlsx";
int num = 1;
while (File.Exists(Path.Combine(directory, string.Format(fileName, num))))
    num++;
var newExcelFile = new FileInfo(Path.Combine(directory, string.Format(fileName, num)));

In general the static File methods are more efficient than always creating a FileInfo instance.