textbox1 と textbox2 の値が入力されたときに textbox1-textbox2 を計算して、textbox3 の値を自動的に取得する方法。
<asp:TextBox ID="txtbox1" runat="server"></asp:TextBox>//enter value as 100
<asp:TextBox ID="txtbox2" runat="server"></asp:TextBox>//enter value as 50, Once we enter 50 result should appear in textbox3
<asp:TextBox ID="txtbox3" runat="server"></asp:TextBox>//Once we enter 50 result should appear in textbox3
txtbox3.Text = (Convert.ToInt32(txtbox1.Text) - Convert.ToInt32(txtbox2.Text)).ToString();