Formating numbers

[BrassicaNigra]

Greetings,

I am writing an application that prepares a quotation for a customer. The
calculations are done in a SQL Server stored procedure. I use a datareader
to fetch the record, but cannot seem to get the data to format correctly.
Since it is a quote I want the data in the format 12.34. Everything seems
fine, except when I have a a zero at the end of the price, then I get 12.3.
It needs to be 12.30.

When I set the textbox value using the datareader I was using the ToString()
function to convert the data from a floating point to a string. Usually when
I do this I can apply a format string as an argument (i.e. ToString("F2")).
When I use the ToString method of the datareader it does not allow for any
arguments.

Can't seem to find any information about this. I have spent more time
trying to format these prices than I have writing the entire application.
What happened to simple data formatting (like the old sprintf())?

Help!

Dale Hoffman

 

[Göran Andersson]

Greetings,

I am writing an application that prepares a quotation for a customer. The
calculations are done in a SQL Server stored procedure. I use a datareader
to fetch the record, but cannot seem to get the data to format correctly.
Since it is a quote I want the data in the format 12.34. Everything seems
fine, except when I have a a zero at the end of the price, then I get 12.3.
It needs to be 12.30.

When I set the textbox value using the datareader I was using the ToString()
function to convert the data from a floating point to a string. Usually when
I do this I can apply a format string as an argument (i.e. ToString("F2")).
When I use the ToString method of the datareader it does not allow for any
arguments.

You should not use the ToString method of the data reader, it will most
likely just return the type name of the data reader object anyway. You
should use the ToString method on the data that you read from the data
reader.

Example:

SomeTextBox.Text = reader.GetDouble(0).ToString("F2");

Can't seem to find any information about this. I have spent more time
trying to format these prices than I have writing the entire application.
What happened to simple data formatting (like the old sprintf())?

It's hasn't changed very much. Take a look at the string.Format method,
it works pretty much like sprintf, only the formatting syntax is a bit
different.

 

[Steven Cheng [MSFT]]

Hi Dale,

As Goran suggested, you should first get the strong-typed data object(such
as double or int ....), then performing formatting with the "toString"
function fo the strong-typed data object. Here is the number formatting
reference in .net:

#Standard Numeric Format Strings
http://msdn.microsoft.com/en-us/library/dwhawy9k.aspx

BTW, you can also use string.Format function to format multiple output
objects.e.g.

===================
double dv = 343.4343;

Console.WriteLine(string.Format("{0:f3}", dv));
=============

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead


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--------------------

 

[Göran Andersson]

Is there a way to control the precision at run time? Sometimes the
appropriate precision isn't known at compile time.

In C you can print double d with 3 decimal places like this:

printf("%.3f\n", d);

And if the precision needs to be set at run time, you get i decimal
places like this:

printf("%.*f\n", i, d);

I couldn't figure out how to do that in C#, so I had to construct the
control string with a StringBuilder. It worked, but the old fashioned
printf() would have been a lot cleaner.

The .NET formatting doesn't support formatting in the formatting, as the
printf function does. Using string operations to construct a format
string is the way to do it.

If you are formatting just a single value, you can use a ToString
overload instead of the string.Format method:

double dv = 343.4343;
int decimals = 3;
string format = "f" + decimals.ToString();

Console.WriteLine(dv.ToString(format));