1
我在asp.net的學習階段，所以決定做一個在線計算器。問題是當我做一個計算1 + 5 =它根本沒有提供任何輸出。我試過調試。保持變量值
Click button 1 :
first value = 1;
click button + :
first value = null;
click button 5 :
first value = 5
click button =
NOTHING :)
這裏是我的C＃代碼：
public partial class _Default : System.Web.UI.Page
{
string firstOperand;
string secondOperand;
string Operator;
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnOff_Click(object sender, EventArgs e)
{
txtScreen.Enabled = false;
ClearVariables();
}
protected void btnOn_Click(object sender, EventArgs e)
{
txtScreen.Enabled = true;
ClearVariables();
}
private void ClearVariables()
{
firstOperand = "";
secondOperand = "";
Operator = "";
}
protected void Operand(string value)
{
if (value == null) return;
try
{
txtScreen.Text = value;
if (firstOperand == null)
{
firstOperand = value;
}
else
{
if (Operator == null)
{
firstOperand.Insert(firstOperand.Length, value);
}
else
{
secondOperand.Insert(secondOperand.Length, value);
}
}
}
catch (Exception ex)
{
}
}
protected void Num1_Click(object sender, EventArgs e)
{
txtScreen.Text = Num1.Text;
Operand(Num1.Text);
}
protected void Num2_Click(object sender, EventArgs e)
{
txtScreen.Text = Num2.Text;
Operand(Num2.Text);
}
protected void Num3_Click(object sender, EventArgs e)
{
txtScreen.Text = Num3.Text;
Operand(Num3.Text);
}
protected void Num4_Click(object sender, EventArgs e)
{
txtScreen.Text = Num4.Text;
Operand(Num4.Text);
}
protected void Num5_Click(object sender, EventArgs e)
{
txtScreen.Text = Num5.Text;
Operand(Num5.Text);
}
protected void Num6_Click(object sender, EventArgs e)
{
txtScreen.Text = Num6.Text;
Operand(Num6.Text);
}
protected void Num7_Click(object sender, EventArgs e)
{
txtScreen.Text = Num7.Text;
Operand(Num7.Text);
}
protected void Num8_Click(object sender, EventArgs e)
{
txtScreen.Text = Num8.Text;
Operand(Num8.Text);
}
protected void Num9_Click(object sender, EventArgs e)
{
txtScreen.Text = Num9.Text;
Operand(Num9.Text);
}
protected void Num0_Click(object sender, EventArgs e)
{
txtScreen.Text = Num0.Text;
Operand(Num0.Text);
}
protected void btnClr_Click(object sender, EventArgs e)
{
txtScreen.Text = "";
ClearVariables();
}
protected void OpDiv_Click(object sender, EventArgs e)
{
if (firstOperand != null)
{
txtScreen.Text = "";
Operator = OpDiv.Text;
}
}
protected void OpMul_Click(object sender, EventArgs e)
{
if (firstOperand != null)
{
txtScreen.Text = "";
Operator = OpMul.Text;
}
}
protected void OpSub_Click(object sender, EventArgs e)
{
if (firstOperand != null)
{
txtScreen.Text = "";
Operator = OpSub.Text;
}
}
protected void OpAdd_Click(object sender, EventArgs e)
{
if (firstOperand != null)
{
txtScreen.Text = "";
Operator = OpAdd.Text;
}
}
protected void OpEqual_Click(object sender, EventArgs e)
{
if (firstOperand == null && Operator == null)
{
return;
}
else if (firstOperand != null && Operator != null && secondOperand == null)
{
secondOperand = firstOperand;
}
else
{
double num1;
double num2;
try
{
num1 = Double.Parse(firstOperand);
num2 =Double.Parse(secondOperand);
{
switch (Operator)
{
case "+":
num1 += num2;
firstOperand = num1.ToString();
txtScreen.Text = firstOperand;
break;
case "-":
num1 -= num2;
firstOperand = num1.ToString();
txtScreen.Text = firstOperand;
break;
case "/":
if (num2 == 0)
{
txtScreen.Text = "Divison by zero";
}
else
{
num1 /= num2;
firstOperand = num1.ToString();
txtScreen.Text = firstOperand;
}
break;
case "*":
num1 *= num2;
firstOperand = num1.ToString();
txtScreen.Text = firstOperand;
break;
default: txtScreen.Text = "Invalid Operation";
break;
}
}
}
catch (Exception ex)
{
txtScreen.Text = "Not a valid Number";
ClearVariables();
}
}
ClearVariables();
}
protected void OpDot_Click(object sender, EventArgs e)
{
if (firstOperand != null)
{
if (Operator == null)
{
firstOperand.Insert(firstOperand.Length, ".");
}
else
{
secondOperand.Insert(secondOperand.Length, ".");
}
}
}
}
有人能解釋發生了什麼事？以及如何解決相同的問題。
感謝
你有沒有通過您的代碼加強在所有...？任何異常，錯誤？在你的'Operand'函數中，你可以捕獲（Exception ex）'，但不要對異常做任何事情。如果出現問題，我會在「catch」塊中打印。你很難通過查看你的代碼來判斷問題是什麼，使用調試器可能會幫助你更多。 – tnw
我注意到諸如'txtScreen.Text = Num1.Text'這樣的語句是多餘的，看看Operand（）是如何做到這一點的。我很好奇txtScreen.Text屬性是否分配了正確的字符串（例如，「6」）？如果您在OpEqual_Click（）中轉到該分配，是firstOperand ==「6」？或者是Double.Parse的問題？ – DonBoitnott
沒有更多異常和值被正確指定。 – Zigma