I need to convert a the string of a Text box to a Value

glennPattonWork3

Hi All, Stupid Question time. If a value is read to a textbox it is a String, to convert it to a value in the past I have done:

int Value = 0;
Value = Convert.ToInt16(textBox1.Text)

I'm sure of it and then done maths and operations on the Value such as:

if(Value > 1000)
{
MessageBox.Show("Here!");
}

But it won't run in VS2022 it returns a System.Format.Exception error. What have I done? Glenn

Tony Hill

Don't use Convert as any error in the format of the input string will cause an exception. Instead use int.Parse because you can check the result of the parse operation to see if you have entered a valid or invalid string. From memory you should do the following

if (int.Parse(textBox1.Text, out int result))
{
// if parsed ok then the result will be filled with the converted value
}
else
{
// display your error message here
}

Richard Deeming

What value is in the textbox? If it can't be parsed as a short using the current culture settings, then Convert.ToInt16 will throw an exception. You should use TryParse[^] rather than the Convert method to avoid the "can't parse this" exception:

if (int.TryParse(textBox1.Text, out int value))
{
if (value > 1000)
{
MessageBox.Show("Here!");
}
}

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Richard Deeming

You mean TryParse; Parse returns the parsed value or throws an exception. :)

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Tony Hill

I checked that twice and still missed that (Doh)

glennPattonWork3

Hmmm, I'm reading back a sensor, it's giving values all over the show!

private void button1_Click(object sender, EventArgs e)
{
//int value = 0;

// MessageBox.Show(textBox1.Text);

if (int.TryParse(textBox1.Text, out int value))
{
   
    if (value > 1000)
    {
        MessageBox.Show("Here!");
    }
    MessageBox.Show(value.ToString());
}

MessageBox.Show(value.ToString());

}

value is taken as 0, despite textBox1.Text having 1234.56...

Lost User

glennPattonWork3 wrote:

despite textBox1.Text having 1234.56...

But 1234.56 is a Float/Double not an Int; the two are quite different.

jeron1

Maybe try decimal.TryParse()? as the input is not an int.

"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment "Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst "I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle

glennPattonWork3

You are right, but even if make 1234 it still returns a 0...

Lost User

Come on Glen, you need to show us the exact code, and the exact text that you are using.

glennPattonWork3

Thanks, that appears to work! :-D

jeron1

Did the TryParse call succeed, return true?

"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment "Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst "I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle

glennPattonWork3

Hi, This is the code I have been trying to get all afternoon!

private void button1_Click(object sender, EventArgs e)
{
float ForceVal = 0;
//MessageBox.Show(weightTxt.Text);
//ForceVal = Convert.ToDecimal(weightTxt.Text);

	//int.TryParse(weightTxt.Text, out int value);
	decimal.TryParse(weightTxt.Text, out decimal value);
   //  MessageBox.Show(value.ToString());
     if (value > 1000)
     {
         MessageBox.Show("Here!");
     }
     MessageBox.Show(value.ToString());
 
	          
}

I think that should do it. I'm hacking together a test program that interfaces to a Phidget load cell in trying to measure a value that needs to converted to Newtons from Grams (I think!). I hate the fact I wasted so much time trying to get the value to be used out of a darned label. I haven't really done much Windows code (I'm an embedded guy really) since VS2008 was the new kid on the block and times like these it shows! :sigh:

glennPattonWork3

Sort of I had to:

decimal.TryParse(weightTxt.Text, out decimal value);

as I was messing with a floating point number, haven't coded in Windows for a while, man it shows!

jeron1

:thumbsup: Good news!

"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment "Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst "I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle