Tweak in Double.ToString() conversion

I am working on an application which involves lot of arithmetic operations. In this application we heavily make use of double and string interchangeably.
I was facing a problem with conversion between double type to string variables.

Consider below code;

1 2	double d = 30.235312769517968; string convertedValue = d.toString();

If we see the output of convertedValue variable it gives us something like 30.235312769518, which fails the comparison.
To preserve the decimal precision we can make use of ToString() as below;

1	string convertedValue = d.ToString("R");

By default, the return value only contains 15 digits of precision although a maximum of 17 digits is maintained internally. If the value of this instance has greater than 15 digits, ToString returns PositiveInfinitySymbol or NegativeInfinitySymbol instead of the expected number. If you require more precision, specify format with the "G17" format specification, which always returns 17 digits of precision, or "R", which returns 15 digits if the number can be represented with that precision or 17 digits if the number can only be represented with maximum precision.

Note that not all the numbers can be represented exactly...

Aliases doesn’t work always

.Net CTS i.e. Common Type System have defined aliases for primitive data types. This facility is made available for the programmers who come from the programming languages prior to .Net like C++, VB6 etc.C3 makes use of int and long for 32 bit and 64 bit unassigned integer whereas VB makes use of Integer and long for the same.
Lets take a look at CTS memory allocation table for C# and C++;

CTS type	Size	C# alias	Type equivalent in C++
System.Int32	4 bytes	int	int or long
System.Int64	8 bytes	long	_ _int64
System.Char	2 bytes	char	WCHAR
System.Double	8 bytes	double	double

Now from the table above it is clear that C# makes use of int as an alias for 32 bit unassigned integer and C++ makes use of int or long. But long in case of C# is 64 bit unassigned integer.

Now you might ask what does that make difference. Let's have a look at it by an example.
We will call beep() function from an unmanaged code with its required arguments.
VB6 prototype is;
Beep(dwFreq as Long, dwDuration as Long) as Boolean
Now if we write it in .net, we might pass arguments as ;
Beep(long dwFreq,long dwDuration)
Now in this case long for VB is 32 bit unassigned integer and long for C# is 64 bit unassigned integer. The function will never return any output because of expected type mismatch.
If you are having any doubts about types in your mind, it is always a good practice to make use qualified names from CTS.

Ref: .Net Gotchas