unable to convert string to float in asp.net c#

Question

I'm trying to calculate the difference of sales and expenses from the database values that I have returned. But when I use a - b it throws the below error. Although I'm converting the double it still gives the error:

cannot implicitly convert type string to double

This is my code:

double a = Double.Parse(reader["sales"].ToString().Trim());
double b  = Double.Parse(reader["expenses"].ToString().Trim());

Label11.Text = a - b;

Any help will be appreciated.

When you debug, are a and b properly doubles? Have you tried doing Label11.Text = (a-b).ToString();? — Tawnos
– Tawnos, Commented Jul 8, 2013 at 17:33
both are returning double but adding that worked perfectly.. thanks — user2561472
– user2561472, Commented Jul 8, 2013 at 17:42

Grant Thomas · Accepted Answer · 2013-07-08 17:33:10Z

6

Because Text is of type string and the values obviously aren't (and therefore neither is the resulting value) of that type:

Label11.Text = (a - b).ToString();

answered Jul 8, 2013 at 17:33

Grant Thomas

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Comments

keyboardP · Accepted Answer · 2013-07-08 17:48:03Z

0

Unless you're sure that you're always going to have valid double values in the string then you might want to use TryParse instead in order to ensure no exceptions are thrown.

double a;
double b;

if (double.TryParse(reader["sales"].ToString().Trim(), out a))  
if (double.TryParse(reader["expenses"].ToString().Trim(), out b))        
    Label11.Text = (a - b).ToString(); //only called if both doubles were parsed

answered Jul 8, 2013 at 17:48

keyboardP

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Comments

DimaSan · Accepted Answer · 2016-12-06 14:34:19Z

0

Instead of: Label11.Text = a - b;
use Label11.Text = (a - b).ToString();

edited Dec 6, 2016 at 14:34

DimaSan

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answered Jul 8, 2013 at 17:35

Md Nasimul Haq

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