Get Int Value From Textbox, Suppose I Enter In 5 Then Result Will Be 1,2,3,4,5... ?

I will show you the way, but you have to put in effort to do it yourself:
1. Create a textbox in the winform to let user enter an integer number, say 5
2. Create a loop that starts from 1 to that integer number
3. At each loop, say at the 3rd loop, convert the current loop count (3) to string and concatenate it with the previous loop counts (1,2), e.g. 1,2,3
4. At the end of the whole loop, show the result in a message box, e.g. 1,2,3,4,5
The End.
Refer:
1. For Loop[^]
2. Messagebox-show[^]
3. Integer to String conversion and string concatenation, Ask Google.