Simple math operation C# -

i have button, textbox , 1 label. want create when user click on button number in label must + number textbox. , can unlimited time.

example first insert 100 label1.text = 100, second insert 300 label.text = 400, third enter 700 label.text = 1100 ...

how without define new variable every click?

you need not have new variable instead of append existing textbox value label

label1.text = convert.tostring(int.parse(label1.text) + int.parse(textbox1.text)); 

happy coding