例1：计算器
try
{
double a = Convert.ToDouble(TextBox1.Text);
double b = Convert.ToDouble(TextBox2.Text);
if (DropDownList1.SelectedValue == "加")
{
Label1.Text = Convert.ToString(a+b);
}
else if (DropDownList1.SelectedValue == "减")
{
Label1.Text = Convert.ToString(a - b);
}
else if (DropDownList1.SelectedValue == "乘")
{
Label1.Text = Convert.ToString(a * b);
}
else
{
Label1.Text = Convert.ToString(a/b);
}
}
catch
{
Label1.Text = "请输入数字";
}
例2：数字乘法表
Label1.Text = "";
int sum = 0;
for (int i = 1; i <= 9; i++)
{
for (int j = 1; j <= i; j++)
{
sum = i * j;
Label1.Text +=i.ToString()+"x"+j.ToString()+"="+sum.ToString()+" ";
}
Label1.Text +="</br>";
}
例3：乘法口诀表
Label1.Text = "";
int sum = 0;
string[] biao = { "十", "一", "二", "三", "四", "五", "六", "七", "八", "九" };
string s1;
string s2;
for (int i = 1; i <= 9; i++)
{
for (int j = 1; j <= i; j++)
{
sum = i * j;
if (sum < 10)
{
Label1.Text += biao[i] + biao[j] + "得" + biao[sum] + " ";
}
else
{
if (sum % 10 != 0)
{
s1 = sum.ToString().Substring(0, 1);
s2 = sum.ToString().Substring(1, 1);
Label1.Text += biao[i] + biao[j]+biao[Convert.ToInt32(s1)] +"十"+ biao[Convert.ToInt32(s2)] + " ";
}
else
{
s1 = sum.ToString().Substring(0, 1);
s2 = sum.ToString().Substring(1, 1);
Label1.Text += biao[i] + biao[j]+ biao[Convert.ToInt32(s1)]+biao[Convert.ToInt32(s2)] + " ";
}
}
}
Label1.Text += "</br>";
