'double'不包含'Text'的定义，也没有扩展方法

Question

Me and my teacher cannot figure this out. It's a windows forms app with all the appropriate fields linked, this is my only issue.

Error 1 'double' does not contain a definition for 'Text' and no extension method

here's my code:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void calculate_Click(object sender, EventArgs e)
    {
        double total = 0; //total amount
        double tip = 0; //tip percentage
        double meal = 0; //meal amount

        tip = Convert.ToDouble(tip.Text) / 100;
        meal = Convert.ToDouble(meal.Text);
        total = (meal * tip);
        total.Text = "$ " + Convert.ToString(total);
    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }
}

Answer 1

I think you are trying to display the result into a Textbox; but Here in the code you declared total as double. please use the textbox name here ( total.Text ) in place of the variable total ; And also use .ToString() instead of .Text inside your Convert.ToDouble(

Few more tips for you:

• use double.TryParse for converting string to double
• use total.ToString("$#00.00"); to get the the number prefixed with a $ symbol and rounded to 2 digits after the decimal

Let me assume the UI elements are :

 //txtTip be the Textbox for tip percentage
 //txtMeal be the Textbox for meal amount
  //txtTotal be the Textbox for Total Amount

Then your code will be like the following:

   double total = 0; //total amount
    double tip = 0; //tip percentage
    double meal = 0; //meal amount
      if(! double.TryParse(txtTip.Text,out tip))
      {
          // show conversion failed error
      }
       if(! double.TryParse(txtMeal.Text,out meal))
      {
          // show conversion failed error
      }
    tip = tip / 100;       
    total = (meal * tip);
    txtTotal.Text =total.ToString("$#00.00")  ;

Answer 2

It looks like you named your class-level Textboxes the exact same as your method-scoped variables. Or at least, that's my best assumption without knowing what your textboxes are actually called.

Your problem is you are trying to find a property Text on a double , which certainly does not exist. If you actually did name your textboxes the same (which is legal in C#), you'll want to reference them by using this.total and this.tip when trying to set the Text property.

It's worth noting that I'm concerned for your education if your teacher is unable to debug this.

Answer 3

I think this is a mistake of use local variable and global variable.

class Test
{
    // global variable.
    int va = 1;
    int vb = 2;

    public void local()
    {
        bool va = false;   // local variable
        Console.WriteLine(va);  // va is bool here.use local value.
        Console.WriteLine(vb); // vb is int, use global value.
    }
}

in your code, you declared local variables.

public partial class Form1 : Form
{
    private void calculate_Click(object sender, EventArgs e)
    {
        // declare local variables...
        // overwrite global varables.
        double total = 0; //total amount
        double tip = 0; //tip percentage
        double meal = 0; //meal amount

        // maybe, you want to invoke textbox.Text.
        // but, tip(TextBox) object is overwrote by double.
        // double has not the Text property, throw exception.
        tip = Convert.ToDouble(tip.Text) / 100; 
        meal = Convert.ToDouble(meal.Text);
        total = (meal * tip);
        total.Text = "$ " + Convert.ToString(total);
    }
}

how to fix it? just declare different variable name, like this:

private void calculate_Click(object sender, EventArgs e)
{
    // make the local variable name is different with global.
    double d_total = 0; //total amount
    double d_tip = 0; //tip percentage
    double d_meal = 0; //meal amount

    d_tip = Convert.ToDouble(tip.Text) / 100;  // tip is TextBox here
    d_meal = Convert.ToDouble(meal.Text);
    d_total = (d_meal * d_tip);
    total.Text = "$ " + Convert.ToString(d_total);
}

or use this like this:

private void calculate_Click(object sender, EventArgs e)
{
    double total = 0; //total amount
    double tip = 0; //tip percentage
    double meal = 0; //meal amount

    tip = Convert.ToDouble(this.tip.Text) / 100;
    meal = Convert.ToDouble(this.meal.Text);
    total = (meal * tip);
    this.total.Text = "$ " + Convert.ToString(total);
}