在 c# 应用程序中选择不同的转换

Question

我有一个转换长度的 c# 应用程序。如果用户输入以点分隔的数字 (3.45)，则应用程序可以正常工作并给出正确的结果，但如果用户输入逗号 (3,45)，则会给出错误的结果。有谁知道我如何解决这个问题

    private void butCal_Click(object sender, EventArgs e)
    {
        // initialising and declaring variables 

        double miles, kilometres, feet, metres, inches, centimetres = 0;

        // the if statements initiates an event handler to select items from the conversions (combobox) to do conversion

        if (Conversions.Text == "Miles to Kilometres")
        {
            if (!double.TryParse(txtNumber.Text, out miles)) // verifies that the string entered is a number
            {
                MessageBox.Show("Please enter a number !"); // displays message if no number is entered
            }

            // Logic for doing calculations
            kilometres = miles * 1.6093; 
            txtAnswer.Text = kilometres.ToString("N2") + " Kilometres"; // displays the answer and rounds it off to two decimals

            txtAnswer.Visible = true;
            txtAnswer.Enabled = false;
            lblAnswer.Text = " Answer = ";
            lblAnswer.Visible = true;
        }

        else if (Conversions.Text == "Kilometres to Miles")
        {
            if (!double.TryParse(txtNumber.Text, out kilometres))
            {
                MessageBox.Show("Please enter a number.");
            }
            miles = kilometres * 0.621;
            txtAnswer.Text = miles.ToString("N2") + " miles ";

            txtAnswer.Visible = true;
            txtAnswer.Enabled = false;
            lblAnswer.Text = " Answer = ";
            lblAnswer.Visible = true;
        }
        else if (Conversions.Text == "Feet to Metres")
        {
            if (!double.TryParse(txtNumber.Text, out feet))
            {
                MessageBox.Show("Please enter a number.");
            }
            metres = feet * 0.3048;
            txtAnswer.Text = metres.ToString("N2") + " metres ";

            txtAnswer.Visible = true;
            txtAnswer.Enabled = false;
            lblAnswer.Text = " Answer = ";
            lblAnswer.Visible = true;
        }

        else if (Conversions.Text == "Metres to Feet")
        {
            if (!double.TryParse(txtNumber.Text, out metres))
            {
                MessageBox.Show("Please enter a number.");
            }
            feet = metres * 3.280839895;
            txtAnswer.Text = feet.ToString("N2") + " Ft ";

            txtAnswer.Visible = true;
            txtAnswer.Enabled = false;
            lblAnswer.Text = " Answer = ";
            lblAnswer.Visible = true;
        }

        else if (Conversions.Text == "Inches to Centimetres")
        {
            if (!double.TryParse(txtNumber.Text, out inches))
            {
                MessageBox.Show("Please enter a number.");
            }
            centimetres = inches * 2.54;
            txtAnswer.Text = centimetres.ToString("N2") + " cm ";
        }

        else if (Conversions.Text == "Centimeters to Inches")
        {
            if (!double.TryParse(txtNumber.Text, out centimetres))
            {
                MessageBox.Show("Please enter a number.");
            }
            inches = centimetres * 0.3937;
            txtAnswer.Text = inches.ToString("N2") + " Inches ";

            txtAnswer.Visible = true;
            txtAnswer.Enabled = false;
            lblAnswer.Text = " Answer = ";
            lblAnswer.Visible = true;
        }
    }

    private void button1_Click(object sender, EventArgs e)
    {
        // resetting all labels, text fields and the conversion (combobox)
        Conversions.SelectedIndex = -1;
        txtNumber.Clear();
        txtAnswer.Clear();
        butCal.Visible = false;

        // Hidding text fields and labels until they are called
        txtAnswer.Visible = false;
        txtNumber.Visible = false;
        lblAnswer.Visible = false;
        lblNumber.Visible = false;
    }

    private void butExit_Click(object sender, EventArgs e)
    {
        Close(); // exits the application
    }

Answer 1

double.TryParse 具有采用文化或数字样式的重载。

http://msdn.microsoft.com/en-us/library/3s27fasw(v=vs.110).aspx

对于IFormatProvider provider 参数，您可以使用 CultureInfo.InvariantCulture 作为点

Answer 2

如果您专门谈论 (3,45)，则可以抛出错误，因为 3,45 可能没有任何意义。如果您希望它正常工作，则使用@selman22 的解决方案，否则，如果您确认用户输入的输入将是标准之一，即 , 将用于分隔数千个，则使用此处给出的解决方案@987654321 @ 类似于 double 或 @Softlion 给出的解决方案

Answer 3

var text = txtNumber.Text;
if(text.IndexOf(',') > 0)
{
   text = text.Replace(',','.');
}

Answer 4

考虑到您的要求。你可以试试下面的方法

   try
{
    double.Parse(txtNumber.Text, CultureInfo.InvariantCulture)
}
catch(Exception ae)
 {
            MessageBox.Show("Not a Number")
 }