请教个小问题。。。。。。
这是我的后台代码，没有错的，能运行。

[解决办法]
放构造函数里

protected void btc()         
{             
int normalTemperature = Convert.ToInt16(DropDownList1.SelectedItem.Text);             
int addTemperature = Convert.ToInt16(DropDownList2.SelectedItem.Text);             double materialValue = Convert.ToDouble(DropDownList3.SelectedItem.Value);             
int equipmentQuantity = Convert.ToInt16(TextBox2.Text);             
int normalMoisture = Convert.ToInt16(DropDownList5.SelectedItem.Text);             int addMoisture = Convert.ToInt16(DropDownList6.SelectedItem.Text);              
 
int targetMTBF = Convert.ToInt16(TextBox3.Text);               
double power1 = materialValue / normalTemperature - materialValue / addTemperature;             
double power2 = (normalMoisture * normalMoisture)/10000 - (addMoisture * addMoisture)/10000;             
double moutiplier = Math.Pow(2.18, power1);             
double montiplicand = Math.Pow(2.18,power2);             
double af = moutiplier * montiplicand;               
double t=targetMTBF/(equipmentQuantity*af);               
TextBox1.Text = t.ToString();         
}
 protected void Button2_Click(object sender, EventArgs e)         
{  
          btc(); 
 }

[解决办法]
在事件外面定义变量，在事件中赋值。