Converting Strings in C# - c#-4.0

Question

I want to convert my string value to int16 and only show 2 decimal places. I have tried the below, but it throws an error as my string value is not actually converted?
namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
string number1 = "1234.00011";
Console.Write(number1);
Console.WriteLine();
string r = String.Format("{0:F2}", number1);
Console.Write(Convert.ToInt16(r));
}
}
}
EDIT
The line that throws the error is
Console.Write(Convert.ToInt16(r));
And the error is
An unhandled exception of type 'System.FormatException' occurred in mscorlib.dll
Additional information: Input string was not in a correct format.

Answer 1

Your call to string.Format is using a floating point format specifier and providing a string argument. These are mutually incompatible. As a result, the string argument is inserted as-is into the result, and stored in r, so that you don't get the desired two-digit rounding you're looking for.
What you likely want to do is something like this:
static void Main(string[] args)
{
string number1 = "1234.00011";
Console.Write(number1);
Console.WriteLine();
var r1 = float.Parse(number1);
string r = String.Format("{0:F2}", r1);
Console.WriteLine(r);
Console.Write((int)r1);
Console.ReadKey();
}
In my tests, it produces the following output:
1234.00011
1234.00
1234
Note that the second line has the desired rounding, because we provided a floating point value to string.Format, so that {0:F2} would work properly. The third line has no decimal places, because we used a direct cast and includes no floating point digits whatsoever.