Input string was not in a correct format là gì năm 2024

Question

I am getting error c# system.FormatException: 'Input string was not in a correct format.' for the below code. I have tried several threads with similar heading still could not find a solution. Please help.

What I have tried:

private void txtDiscount_TextChanged(object sender, EventArgs e)

    {  
        double FinalFee;  
        double CourseFee1;  
        double Disc;  
        CourseFee1 = Convert.ToDouble(lblCourseFee.Text);  
        Disc = Convert.ToDouble(txtDiscount.Text);  
        FinalFee = CourseFee1 - (CourseFee1 * (Disc / 100));            
        if (Disc > 40)  
        {  
            string message = "Maximum Discount is 40% ";  
            string title = "Discount Maximum Limit Exceeded";  
            MessageBoxButtons buttons = MessageBoxButtons.OK;  
            DialogResult result = MessageBox.Show(message, title, buttons, MessageBoxIcon.Warning);  
        }  
        else  
        {  
            lblFinalFee.Text = FinalFee.ToString("N2");  
        }  
    }

Never use Convert methods with user input: they throw an exception if the user mistypes. Instead, use the double.TryParse method which returns an error:

double courseFee; if (!double.TryParse(lblCourseFee.Text, out courseFee)) { ... report problem to user ... return; } double disc; if (!double.TryParse(txtDiscount.Text, out disc)) { ... report problem to user ... return; } double finalFee = courseFee - courseFee * disc / 100.0;

Error is on line

Disc = Convert.ToDouble(txtDiscount.Text); OR CourseFee1 = Convert.ToDouble(lblCourseFee.Text);

because you are converting value into double. Verify you are giving the correct numeric value. There ould be a change a character or any other character coming into this filed which cause an error.

Thanks everyone for your valuable inputs. I solved the issue with below code.

bool valid1 = float.TryParse(lblCourseFee.Text, out CourseFee);

bool valid2 = float.TryParse(txtDiscount.Text, out Disc);

Found it on another website. Serves the purpose. Thanks again.

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là ai Hỏi Đáp Là gì For input string