I have approximately 15 textboxes that I want to sum together.

I have tried textbox1.Text + Textbox2.Text but this just concatenates the numbers together.

I can get this to work by creating mulitple variables of type integer and then setting each textbox value as a seperate variable and then adding the variables together but this seems excessive.

You need to cast the .Text value to an integer. There's nothing excessive about that. That's what you get with a strongly typed language.

Maybe to make it a bit easier to write and run, you could add all the textboxes to a generic list:

   List<TextBox> lstTextBoxes = new List<TextBox>();
   lstTextBoxes.Add(textBox1);
   ...

then loop thru the list to add everything up:

   int intTotal = 0;
   for(int i = 0; i < lstTextBoxes.Count; i++){
      intTotal += int.Parse(lstTextBoxes[i].Text);
   }

Of course, you'll want to catch formatting errors and such.

-Peter