當texboxes爲空時顯示驗證錯誤

Question

 double HP, L, hr, Est, eee, result; 
     string output; 
     HP = double.Parse(textBox1.Text); 
     L = double.Parse(textBox2.Text); 
     hr = double.Parse(textBox3.Text); 
     Est = double.Parse(textBox4.Text); 
     eee = double.Parse(textBox5.Text); 

     result = HP * (L/100) * 0.746 * hr * (((1/Est) - (1/eee)) * 100); 
     output = " " + result; 

     textBox6.Text = output;   

我想在一個或多個文本框爲空時顯示驗證消息。

Answer 1

驗證字段不爲空：

if(!String.IsNullOrEmpty(textBox.Text) && String.IsNullOrEmpty(...)){ 

} 

檢查是值是有效的double：

double parsedValue; 

if (!double.TryParse(textBox.Text, out parsedValue)) 
{ 
    MessageBox.Show("This is a double only field"); 
    return; 
} 

---

你會得到這樣的事情：

if(nullorempty tests){ 
    if(youcanparse first textbox){ 
     the value of that textbox is not valid 
    } else if(youcanparse second textbox){ 
     ... 
    } 
} else { 
    show "you must enter something !" 
} 

等