Trying to multiply and get the sum of result into a textbox using TextChanged as event

Question

I'm new to using C# and Visual Studio and i'm having a problem.

I'm trying to calculate a total value of three different multiplications using TextChanged event, so the total textbox updates every time I input a number in the textboxes I am using for the multiplications.

The total result in textbox4 is always 0. What am I doing wrong here?

Here is my code

    public double multip_result1;
    public double multip_result2;
    public double multip_result3;

    public void textbox1_TextChanged(object sender, EventArgs e)
    {
       double a, b, multip_result1;
       a = Double.Parse(textbox1.Text);
       b = 4.50;

       multip_result1 = a * b;

       total();
    }

    public void textbox2_TextChanged(object sender, EventArgs e)
    {
        double d, f, multip_result2;
        d = double.Parse(textbox2.Text);
        f = 6.50;

        multip_result2 = d * f;

        total();
    }

    public void textbox3_TextChanged(object sender, EventArgs e)
    {
        double h, j, multip_result3;
        h = double.Parse(textbox3.Text);
        j = 8.50;

        multip_result3 = h * j;

        total();
    }

    public void total() 
    {
        double total_sum;
        total_sum = multip_result1 + multip_result2 + multip_result3;
        textbox4.Text = total_sum.ToString();
    }

Declaring a variable inside a method with the same name of a global variable has the effect to hide the global variable. You never assign a value to the global variables declared at the init of your code and used inside the _total_ — Steve, Dec 13 '17 at 16:19

Tim Schmelter · Accepted Answer · 2017-12-13T16:23:23.507

5

You have local variables multip_result1, multip_result2, multip_result3 which hide the fields with the same names, just remove them from the event handlers. So f.e. this:

double a, b, multip_result1;

becomes

double a, b;

otherwise you assign the calculated value to this local variable and the field remains 0.

If you want to assign to the field with the same name you could also use this.fieldName. But i'd strongly advise against using the same name to avoid issues like this.

edited Dec 13 '17 at 16:23

answered Dec 13 '17 at 16:19

Tim Schmelter

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I can't believe it was something as simple as this! Thank you! – MCoyle Dec 13 '17 at 16:22

score 0 · Answer 2 · answered Dec 13 '17 at 16:48

In each of your change functions you're initializing multip_result1, multip_result2, and multip_result3.

This means it's not setting the more public versions, so when "total()" runs, all values are still zero.

"double a, b, multip_result1;" should be "double a, b;" and update the other functions accordingly.

Trying to multiply and get the sum of result into a textbox using TextChanged as event

2 Answers2