Formatting data in a textbox in C#

Question

I've got a dropdown control on a form. The results of this dropdown need to be written to a hidden textbox, but when they're written to the textbox it needs to be in the format "XX.XX". So, if the user selects "1.0", it needs to be written to the textbox as "01.00".

I'm a native Access/VBA programmer, and it's fairly easy to do in VBA. How would I do this in C# code-behind?

What I have now is:

 protected void ddlCIT_SelectedIndexChanged(object sender, EventArgs e) { txtCIT.Text = ddlCIT.SelectedValue; }

This was before I knew about this requirement., so it doesn't address the formatting issue at all. I'm sure it's got to be something like:

txtCIT.Text = Format(ddlCIT.SelectedValue, "##.##");

or something, but I just can't figure it out. None of the examples I've found were doing anything close to what I need.

EDIT

As per asven's answer, I've now got the following code:

 string ddlCITVal = ddlCIT.SelectedValue.ToString(); txtCIT.Text = string.Format("{0:#0.0#}", ddlCITVal); string blearg = string.Format("{0:0.0#}", ddlCITVal);

Both my textbox and my string "blearg" show a result of "2.0" in the Immediate window when I select "2.0" from the dropdown. I also tried using "{0:00.00}" in the format clause with identical results.

I'm using VS2012 if that matters.

Can you tell me, given the above information, what the actual line of code would be? I'm really still a C# novice. — Johnny Bones
– Johnny Bones, Commented Sep 24, 2014 at 18:03

asven · Accepted Answer · 2014-09-24 18:14:57Z

3

Try

string.Format("{0:00.00}", ddlCIT.SelectedValue);

edited Sep 24, 2014 at 18:14

answered Sep 24, 2014 at 18:01

asven

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6 Comments

Nick O Over a year ago

Your missing quotes around {0:00.00}.

Johnny Bones Over a year ago

It's not working. Do you think I have to convert ddlCIT.SelectedValue to a string or something? Right now the textbox is still identical to what's in the dropdown.

asven Over a year ago

You can try to just do ddlCIT.SelectedValue.ToString()

Nick O Over a year ago

@JohnnyBones You shouldn't have to convert it to a string. Is your drop down list bound to an array of strings or objects? If it is just a list of strings your may want to try string.Format("{0:00.00}", ddlCIT.Text);.

Johnny Bones Over a year ago

Does it matter that I'm using C# 2012? Because it's still keeping the same format as the dropdown.

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tinstaafl · Accepted Answer · 2014-09-24 19:12:32Z

You could go one step further and use a custom textbox. This allows you to have validation and formatting built in:

public class NumDoubTextbox : TextBox { public override string Text { get { return base.Text; } set { double temp = 0; if (double.TryParse(value, out temp)) //Formatting as a float then padding left with 0's should give the format you want base.Text = temp.ToString("F2").PadLeft(5,'0'); else //Handle invalid input here. base.Text = "--.--"; } } }

You can put this in a separate project and compile it and have it included in the toolbox so that it can be used at design time.

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