C# windows 表格项目除法变量错误

Question

Greeting everyone, I'm trying to do a windows form for collage were I can get the average of student scores. Seems like I have an issue with the divide function. here is my code, to see if you guys spot something wrong that could help me. I Appreciate in advance

    private void getaveragebutton_Click(object sender, EventArgs e)
    {
        if (customTextboxes4.Texts == "" || customTextboxes5.Texts == "" || customTextboxes6.Texts == "" || customTextboxes7.Texts == "" || customTextboxes8.Texts == "" ||
            customTextboxes9.Texts == "" || customTextboxes10.Texts == "" || customTextboxes11.Texts == "" || customTextboxes12.Texts == "" || customTextboxes13.Texts == ""
            || customTextboxes15.Texts == "" || customTextboxes16.Texts == "" || customTextboxes17.Texts == "" || customTextboxes18.Texts == "" || customTextboxes19.Texts == "" ||
            customTextboxes20.Texts == "" || customTextboxes21.Texts == "" || customTextboxes22.Texts == "" || customTextboxes23.Texts == "" || customTextboxes24.Texts == "")
        {
            MessageBox.Show("Fill all the Boxes with Digits");
        }

        else
        {

            label4.Visible = true;
            label5.Visible = true;
            label7.Visible = true;
            label61.Visible = true;
            label28.Visible = true;
            label29.Visible = true;
            label30.Visible = true;
            label31.Visible = true;
            label45.Visible = true;
            label46.Visible = true;


            //short--test calculations

            //students short test score variables
            decimal a, b, c, d, e1, f, g, h, i, j;
            //students short test value variables
            decimal k, l, m, n, o, p, q, r, s, t;
            //st results variables
            decimal u, v;
            decimal r1st;
            decimal r2st;
            decimal results;

            //customboxes st score
            a = Decimal.Parse(customTextboxes4.Texts);
            b = Decimal.Parse(customTextboxes5.Texts);
            c = Decimal.Parse(customTextboxes6.Texts);
            d = Decimal.Parse(customTextboxes7.Texts);
            e1 = Decimal.Parse(customTextboxes8.Texts);
            f = Decimal.Parse(customTextboxes9.Texts);
            g = Decimal.Parse(customTextboxes10.Texts);
            h = Decimal.Parse(customTextboxes11.Texts);
            i = Decimal.Parse(customTextboxes12.Texts);
            j = Decimal.Parse(customTextboxes13.Texts);

            //custom boxes st values
            k = Decimal.Parse(customTextboxes15.Texts);
            l = Decimal.Parse(customTextboxes16.Texts);
            m = Decimal.Parse(customTextboxes17.Texts);
            n = Decimal.Parse(customTextboxes18.Texts);
            o = Decimal.Parse(customTextboxes19.Texts);
            p = Decimal.Parse(customTextboxes20.Texts);
            q = Decimal.Parse(customTextboxes21.Texts);
            r = Decimal.Parse(customTextboxes22.Texts);
            s = Decimal.Parse(customTextboxes23.Texts);
            t = Decimal.Parse(customTextboxes24.Texts);

            r1st = a + b + c + d + e1 + f + g + h + i + j;
            r2st = k + l + m + n + o + p + q + r + s + t;
            //st results variables definitions
            u = Decimal.Parse(label28.Text);
            v = Decimal.Parse(label29.Text);
           
           
            //st result



            label28.Text = r1st.ToString();
            label29.Text = r2st.ToString();
            results = u / v;
            label4.Text = results.ToString();
           
            return;
        }

[ enter image description here ]( https://i.stack.imgur.com/xu8cp.png )

Im trying to get all the score inserted in the text boxes to sum them. then get the results to Student Score and Total (That part is working for me). After that divide the Student Score / Total to get the results in a hidden label that will be visible after getting the results. (that is the part that Im having issues with)

Answer 1

Well sorry to everyone for not following the proper way to post to get the proper help and thanks for those who let me know what to do for a next time to get the proper help. Also, thank you for explaining me the variable thing that was empty I really appreciate. Here is how I did fix my issue:

    private void getaveragebutton_Click(object sender, EventArgs e)
    {
        if (customTextboxes4.Texts == "" || customTextboxes5.Texts == "" || customTextboxes6.Texts == "" || customTextboxes7.Texts == "" || customTextboxes8.Texts == "" ||
            customTextboxes9.Texts == "" || customTextboxes10.Texts == "" || customTextboxes11.Texts == "" || customTextboxes12.Texts == "" || customTextboxes13.Texts == ""
            || customTextboxes15.Texts == "" || customTextboxes16.Texts == "" || customTextboxes17.Texts == "" || customTextboxes18.Texts == "" || customTextboxes19.Texts == "" ||
            customTextboxes20.Texts == "" || customTextboxes21.Texts == "" || customTextboxes22.Texts == "" || customTextboxes23.Texts == "" || customTextboxes24.Texts == "")
        {
            MessageBox.Show("Fill all the Boxes with Digits");
        }

        else
        {

            label4.Visible = true;
            label5.Visible = true;
            label7.Visible = true;
            label61.Visible = true;
            label28.Visible = true;
            label29.Visible = true;
            label30.Visible = true;
            label31.Visible = true;
            label45.Visible = true;
            label46.Visible = true;


            //short--test calculations

            //students short test score variables
            decimal studentscorebox1, studentscorebox2, studentscorebox3, studentscorebox4, studentscorebox5, studentscorebox6, studentscorebox7, studentscorebox8, studentscorebox9, studentscorebox10;
            //students short test value variables
            decimal studentshorttestvalue1, studentshorttestvalue2, studentshorttestvalue3, studentshorttestvalue4, studentshorttestvalue5, studentshorttestvalue6, studentshorttestvalue7, studentshorttestvalue8,
                studentshorttestvalue9, studentshorttestvalue10;
            //st results variables
            
            decimal studentshortestoverallscore;
            decimal shortestoverallvalue;
            decimal shortestaverage;

            //customboxes student short test scores
            studentscorebox1 = Decimal.Parse(customTextboxes4.Texts);
            studentscorebox2 = Decimal.Parse(customTextboxes5.Texts);
            studentscorebox3 = Decimal.Parse(customTextboxes6.Texts);
            studentscorebox4 = Decimal.Parse(customTextboxes7.Texts);
            studentscorebox5 = Decimal.Parse(customTextboxes8.Texts);
            studentscorebox6 = Decimal.Parse(customTextboxes9.Texts);
            studentscorebox7 = Decimal.Parse(customTextboxes10.Texts);
            studentscorebox8 = Decimal.Parse(customTextboxes11.Texts);
            studentscorebox9 = Decimal.Parse(customTextboxes12.Texts);
            studentscorebox10 = Decimal.Parse(customTextboxes13.Texts);

            //student short test value
            studentshorttestvalue1 = Decimal.Parse(customTextboxes15.Texts);
            studentshorttestvalue2 = Decimal.Parse(customTextboxes16.Texts);
            studentshorttestvalue3 = Decimal.Parse(customTextboxes17.Texts);
            studentshorttestvalue4 = Decimal.Parse(customTextboxes18.Texts);
            studentshorttestvalue5 = Decimal.Parse(customTextboxes19.Texts);
            studentshorttestvalue6 = Decimal.Parse(customTextboxes20.Texts);
            studentshorttestvalue7 = Decimal.Parse(customTextboxes21.Texts);
            studentshorttestvalue8 = Decimal.Parse(customTextboxes22.Texts);
            studentshorttestvalue9 = Decimal.Parse(customTextboxes23.Texts);
            studentshorttestvalue10 = Decimal.Parse(customTextboxes24.Texts);

            //Sumatory of Students scores and Sumatory of Test Value
            studentshortestoverallscore = studentscorebox1 + studentscorebox2 + studentscorebox3 + studentscorebox4 + studentscorebox5 + studentscorebox6 + studentscorebox7 + studentscorebox8 + studentscorebox9 + studentscorebox10;
            shortestoverallvalue = studentshorttestvalue1 + studentshorttestvalue2 + studentshorttestvalue3 + studentshorttestvalue4 + studentshorttestvalue5 + studentshorttestvalue6 + studentshorttestvalue7 +
                studentshorttestvalue8 + studentshorttestvalue9 + studentshorttestvalue10;
          

            //String Results to Labels

            label28.Text = studentshortestoverallscore.ToString();
            label29.Text = shortestoverallvalue.ToString();
            //Get Average of Short Test
              shortestaverage = studentshortestoverallscore / shortestoverallvalue * 100;
              label4.Text = shortestaverage.ToString();

            return;
        }

    }

I did a correction of the variable names to not get confused like I was advised in the first post, then I deleted some variables that were empty like someone here explained me (thanks). Finally I did a re order of how it should be calculated to get the average and got it working. thanks to all and if you see something that I can improve let me know. I really appreciate everyone and every single advise. Have a good day everyone.

Answer 2

You cannot convert label to decimal as long as label contains no value. You have to rearrange the lines as follows

        //st result

        label28.Text = r1st.ToString();
        label29.Text = r2st.ToString();

        u = Decimal.Parse(label28.Text);
        v = Decimal.Parse(label29.Text);

        results = u / v;
        label4.Text = results.ToString();
       
        return;