How do I stop the users from using strings in a textbox?

Question

1.00/5 (1 vote)

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C#

<pre lang="c#"><pre lang="c#">

void BMR()
{
    int bmr = 0;
    double weight = Convert.ToInt32(tbWeight.Text);
    double height = Convert.ToInt32(tbHeight.Text);
    double age = Convert.ToInt32(tBAge.Text);
    if (rBMan.Checked)
    {
        bmr = Convert.ToInt32(66.47 + (13.75 * weight) + (5.003 * height) - (6.755 * age));
        lblBMR.Text = lblBMR.Text + bmr;
    }
    else if(rBWoman.Checked)
    {
        bmr = Convert.ToInt32(655.1 + (9.563 * weight) + (1.85 * height) - (4.676 * age));
        lblBMR.Text = lblBMR.Text + bmr;
    }
    else
    {
        MessageBox.Show("Select your Gender first", "Error",MessageBoxButtons.OK, MessageBoxIcon.Error );
    }
}

What I have tried:

I want the program to accept only double values because strings just break it. Thank you in advance with the help!

Posted 30-Sep-20 0:03am

TheJoKr Channel

Updated 30-Sep-20 1:14am

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3 solutions

Solution 2

A better idea is to use a NumericUpDown control instead of a textbox: the value is then always numeric, and always valid / in range.

Posted 30-Sep-20 0:58am

OriginalGriff

Comments

Richard MacCutchan 30-Sep-20 7:08am

For doubles?

OriginalGriff 30-Sep-20 7:32am

All of his code shows Convert.ToInt32

Richard MacCutchan 30-Sep-20 7:38am

Ha, ha, I missed that. So I wonder why he wants double values?

Solution 3

Double.TryParse Method (System) | Microsoft Docs[^]

C#

void BMR()
{
    if (!double.TryParse(tbWeight.Text, out var weight))
    {
        MessageBox.Show("Enter a valid weight", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        return;
    }
    if (!double.TryParse(tbHeight.Text, out var height))
    {
        MessageBox.Show("Enter a valid height", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        return;
    }
    if (!double.TryParse(tBAge.Text, out var age))
    {
        MessageBox.Show("Enter a valid age", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        return;
    }

    int bmr = 0;
    if (rBMan.Checked)
    {
        bmr = Convert.ToInt32(66.47 + (13.75 * weight) + (5.003 * height) - (6.755 * age));
        lblBMR.Text = lblBMR.Text + bmr;
    }
    else if(rBWoman.Checked)
    {
        bmr = Convert.ToInt32(655.1 + (9.563 * weight) + (1.85 * height) - (4.676 * age));
        lblBMR.Text = lblBMR.Text + bmr;
    }
    else
    {
        MessageBox.Show("Select your Gender first", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
}

Posted 30-Sep-20 1:14am

Richard Deeming

Comments

Maciej Los 30-Sep-20 7:38am

5ed!

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Richard MacCutchan · Accepted Answer · 2020-09-30T00:12:00

Solution 1

textbox numeric only - Google Search[^]

Posted 30-Sep-20 0:12am

Richard MacCutchan

Comments

Maciej Los 30-Sep-20 7:38am

5ed!