Check if TextBox input is a decimal number or not - C#

Question

My Goal: I want textbox to accept the decimal numbers like 123.45 or 0.45 or 1004.72. If the user types in letters like a or b or c, the program should display a message alerting the user to input only numbers.

My Problem: My code only checks for numbers like 1003 or 567 or 1. It does not check for decimal numbers like 123.45 or 0.45. How do I make my text box check for decimal numbers? Following is my code:

namespace Error_Testing
{

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

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            string tString = textBox1.Text;
            if (tString.Trim() == "") return;
            for (int i = 0; i < tString.Length; i++)
            {
                if (!char.IsNumber(tString[i]))
                {
                    MessageBox.Show("Please enter a valid number");
                    return;
                }
            }
            //If it get's here it's a valid number
        }
    } 
}

I am a newbie and Thanks for your help in advance. :)

Answer 1

use Decimal.TryParse to check if the string entered is decimal or not.

decimal d;
if(decimal.TryParse(textBox1.Text, out d))
{
    //valid 
}
else
{
    //invalid
    MessageBox.Show("Please enter a valid number");
    return;
}

Answer 2

decimal.Tryparse对于包含“，”字符的字符串返回true，例如，类似“ 0,12”的字符串返回true。

Answer 3

private void txtrate_TextChanged_1(object sender, EventArgs e)
        {
            double parsedValue;
            decimal d;
            // That Check the Value Double or Not
            if (!double.TryParse(txtrate.Text, out parsedValue))
            {
                //Then Check The Value Decimal or double Becouse The Retailler Software Tack A decimal or double value
                if (decimal.TryParse(txtrate.Text, out d) || double.TryParse(txtrate.Text, out parsedValue))
                {
                    purchase();
                }
                else
                {
                    //otherwise focus on agin TextBox With Value 0
                    txtrate.Focus();                  
                    txtrate.Text = "0";                   
                }


            }
            else
            {
                // that function will be used for calculation Like 
                purchase();
                /*  if (txtqty.Text != "" && txtrate.Text != "")
                  {
                      double rate = Convert.ToDouble(txtrate.Text);
                      double Qty = Convert.ToDouble(txtqty.Text);
                      amt = rate * Qty;
                  }*/

            }`enter code here`
        }