Problem:
How can you validate numerics in a .Net Winforms TextBox control.
Resolution:
The keypress event in .Net allows you to trap when a key is pressed on the keyboard and interpret what key was pressed. This allows you ensure that only digits , "." , " " and "-" are entered.
More complex checking can also be performed on the TextChanged Event. This is fired when the Text in a textbox is changed and allows you to check the full text that is in the control.
Some examples of using these events to handle numeric checking is:-
method-id. "textBox1_KeyPress" final private.
linkage section.
01 sender object.
01 e S-W-Forms-KeyPressEventArgs.
procedure division using by value sender e.
set ws-string to e::"KeyChar"
if cChar::"IsControl"(ws-string , 0)
exit method
end-if
if not ( ws-string::"CompareTo"(".") = 0)
if not ( ws-string::"CompareTo"("-") = 0)
if not ( ws-string::"CompareTo"(" ") = 0)
if not (cChar::"IsDigit"(ws-string , 0))
set e::"Handled" to true
invoke cConsole::"Beep"()
end-if
end-if
end-if
end method "textBox1_KeyPress".
method-id. "textBox1_TextChanged" final private.
01 ls-decimal decimal.
linkage section.
01 sender object.
01 e System-EventArgs.
procedure division using by value sender e.
if not decimal::"TryParse"(textBox1::"Text" , ls-decimal) and not textBox1::"Text"::"Length" = 0
set textBox1::"BackColor" to cColor::"Red"
else
set textBox1::"BackColor" to cSystemColor::"Window"
end-if
end method "textBox1_TextChanged".
A working project is attached this this Knowledgebase article.
