CODEWITHSUNDEEP
c#.nettext
John Watter
John Watter

Reputation: 5

Subtract (-) 2 Text Labels from each other to get result

Well, I've tried it with ToInt, ToString, and I'm out of options. I'm trying to substract 2 Label Texts from each other. (Those contains numbers from RSS)

What I have at the moment:

        lblOldID.Text = nodeChannel["oldid"].InnerText;
        lblNewID.Text = nodeChannel["newid"].InnerText;

So let's say oldid contains "500" and newid "530".

But for some reason, I can't substract (-) them. What I want:

      lblResultID.Text = lblOldID.Text - lblNewID.Text;

Example: Result = 530 - 500

So how is that possible?

Upvotes: 0

Views: 2306

Answers (3)

keyboardP
keyboardP

Reputation: 69372

You need to convert the text to ints.

//These are the ints we are going to perform the calculation on
Int32 oldID = 0;
Int32 newID = 0;

//TryParse returns a bool if the string was converted to an int successfully    
bool first = Int32.TryParse(lblOldID.Text, out oldID);
bool second = Int32.TryParse(lblNewID.Text, out newID);

//Check both were converted successfully and perform the calculation
if(first == true && second == true)
{
   lblResultID.Text = (oldID - newID).ToString();
}
else
{
   lblResultID.Text = "Could not convert to integers";
}

TryParse prevents an exception being thrown if the data in the labels cannot be converted to integers. Instead, it returns false (or true if the numbers were parsed successfully).

Upvotes: 3

Icarus
Icarus

Reputation: 63964

Perhaps because you really should parse them:

lblResultID.Text = (int.Parse(lblOldID.Text) - int.Parse(lblNewID.Text)).ToString();

Or in string format:

lblResultID.Text = lblOldID.Text + " - "+ lblNewID.Text;

Upvotes: 0

Michael Petrotta
Michael Petrotta

Reputation: 60942

If you want the label text to be, literally, 530 - 500, concatenate the strings like so:

lblResultID.Text = lblOldID.Text + " - " + lblNewID.Text;

If you want the label text to be the result of subtracting the numbers represented in the labels, convert them to integers first:

int old = Int32.Parse(lblOldID.Text);
int new = Int32.Parse(lblNewID.Text);
lblResultID.Text = (old - new).ToString();

(You'll need some error checking in there if there's the possibility that either value might not convert cleanly to an integer)

Upvotes: 3

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