如何在輸入和檢測到不正確的值後清除並顯示我清除的表格值

Question

我想知道如何清除&在輸入並檢測到錯誤值後顯示（重置）我清除的表格值。目前，當我收到錯誤的輸入時，即使在我再次點擊輸入按鈕後，它仍然在那裏。任何幫助將不勝感激。

namespace Mileage 
    { 
    public partial class Form2 : Form 
    { 
     private double beginMileage, endMileage, gallons, mpg;   

     public Form2() 
     { 
     InitializeComponent(); 
     } 

     //Enter button click 
     public void menuItem1_Click(object sender, EventArgs e) 
     { 
     if (endMileage<beginMileage) 
     { 
      this.label5.Text = String.Format("ERROR: End mileage is less than begining mileage."); 
     } 

     else if((endMileage<0)||(beginMileage<0)) 
     { 
      this.label5.Text = String.Format("ERROR: One or more mileage input is negative.");     
     } 

     else if ((endMileage == 0) || (gallons == 0)) 
     { 
      this.label5.Text = String.Format("ERROR: The end mileage and/or gallon input is zero."); 

     } 

     else 
     { 
      beginMileage = double.Parse(this.textBox1.Text.Replace(" ", "")); 

      endMileage = double.Parse(this.textBox2.Text.Replace(" ", "")); 

      gallons = double.Parse(this.textBox3.Text.Replace(" ", "")) ; 

      mpg = ((endMileage - beginMileage)/gallons); 

      this.label5.Text = String.Format("{0}", mpg); 
     } 

    } 

    //exit button click 
    public void menuItem2_Click(object sender, EventArgs e) 
    { 
     Application.Exit();    

    } 
} 

}

Answer 1

嗯。 。 。所以我想通了。這僅僅是一個邏輯錯誤，我做了:)

namespace Mileage 
{ 
    public partial class Form2 : Form 
    { 
    private float beginMileage, endMileage, gallons, mpg;   

    public Form2() 
    { 
     InitializeComponent(); 
    } 

    public void menuItem1_Click(object sender, EventArgs e) 
    { 
     beginMileage = float.Parse(this.textBox1.Text.Replace(" ", "")); 

     endMileage = float.Parse(this.textBox2.Text.Replace(" ", "")); 

     gallons = float.Parse(this.textBox3.Text.Replace(" ", "")); 

     if((endMileage<0)||(beginMileage<0)||(gallons<0)) 
     { 
      this.label5.Text = String.Format("ERROR: One or more input(s) is negative."); 
      this.textBox1.Text = " "; 
      this.textBox2.Text = " "; 
      this.textBox3.Text = " "; 
     } 

     else if ((endMileage == 0) || (gallons == 0)) 
     { 
      this.label5.Text = String.Format("ERROR: The end mileage and/or gallon input is zero."); 
      this.textBox1.Text = " "; 
      this.textBox2.Text = " "; 
      this.textBox3.Text = " ";     
     } 

     else if (endMileage < beginMileage) 
     { 
      this.label5.Text = String.Format("ERROR: End mileage is less than begining mileage."); 
      this.textBox1.Text = " "; 
      this.textBox2.Text = " "; 
      this.textBox3.Text = " "; 

     } 
     else 
     {        
      mpg = ((endMileage - beginMileage)/gallons); 
      this.label5.Text = String.Format("{0}", mpg); 
     } 

    } 

    public void menuItem2_Click(object sender, EventArgs e) 
    { 
     Application.Exit();    

    } 
} 

}