I am having three text boxes as below

14y1.4kVisual Basic .NET

i am having three text boxes as below

Rent textbox

service tax textbox

Gross rent textbox

i am adding rent and serice tax output will be displayed in gross rent.

i write caluation code in txt_tax as below

private void txt_tax_TextChanged(object sender, EventArgs e)

{

int a, b, c;

a = Convert.ToInt32(txt_rent.Text);

b = Convert.ToInt32(txt_tax.Text);

c = a + b;

txt_grossrent.Text = c.ToString();

}

for example i type service tax amount as 1000 then i clear the 1000 amount

the error occurs as Input string was not in a correct format.

please help me.please give the correct code.

Regards

Narsiman

2 Replies

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Vulpes14y ago
Yes, int.TryParse would be better here as you can then pinpoint errors and ask the user to make an alteration. You can also check for negative values at the same time:

Try:

private void txt_tax_TextChanged(object sender, EventArgs e)
{
int a, b, c;

if (!int.TryParse(txt_rent.Text, out a) || a < 0)
{
MessageBox.Show("Not a valid number. Please reenter.");
txt_rent.Focus();
return;
}

if (!int.TryParse(txt_tax.Text, out b) || b < 0)
{
MessageBox.Show("Not a valid number. Please reenter.");
txt_tax.Focus();
return;
}

c = a + b;
txt_grossrent.Text = c.ToString();
}
14y ago
int a,b,c=0;
if (!string.IsNullOrEmpty(txt_rent.Text))
a = Convert.ToInt32(txt_rent.Text);
if (!string.IsNullOrEmpty(txt_tax.Text))
b = Convert.ToInt32(txt_tax.Text);

c= a+b;

txt_grossrent.Text =Convert.ToString(c);

Please try this code.

Before doing the Convert.ToInt32 check the value of input. whether it is null or empty. Otherwise you can use, Int.tryparse method also for Convert.ToInt32 function.