CODEWITHSUNDEEP
c#typesinttype-conversionlong-integer
Ian G
Ian G

Reputation: 30234

Can I convert long to int?

I want to convert long to int.

If the value of long > int.MaxValue, I am happy to let it wrap around.

What is the best way?

Upvotes: 180

Views: 292083

Answers (8)

Andre
Andre

Reputation: 366

A possible way is to use the modulo operator to only let the values stay in the int32 range, and then cast it to int.

var intValue= (int)(longValue % Int32.MaxValue);

Upvotes: 14

nzrytmn
nzrytmn

Reputation: 6941

It can convert by

Convert.ToInt32 method

But it will throw an OverflowException if it the value is outside range of the Int32 Type. A basic test will show us how it works:

long[] numbers = { Int64.MinValue, -1, 0, 121, 340, Int64.MaxValue };
int result;
foreach (long number in numbers)
{
   try {
         result = Convert.ToInt32(number);
        Console.WriteLine("Converted the {0} value {1} to the {2} value {3}.",
                    number.GetType().Name, number,
                    result.GetType().Name, result);
     }
     catch (OverflowException) {
      Console.WriteLine("The {0} value {1} is outside the range of the Int32 type.",
                    number.GetType().Name, number);
     }
}
// The example displays the following output:
//    The Int64 value -9223372036854775808 is outside the range of the Int32 type.
//    Converted the Int64 value -1 to the Int32 value -1.
//    Converted the Int64 value 0 to the Int32 value 0.
//    Converted the Int64 value 121 to the Int32 value 121.
//    Converted the Int64 value 340 to the Int32 value 340.
//    The Int64 value 9223372036854775807 is outside the range of the Int32 type.

Here there is a longer explanation.

Upvotes: 3

Clement
Clement

Reputation: 4297

The following solution will truncate to int.MinValue/int.MaxValue if the value is out of Integer bounds.

myLong < int.MinValue ? int.MinValue : (myLong > int.MaxValue ? int.MaxValue : (int)myLong)

Upvotes: 5

R&#233;my Esmery
R&#233;my Esmery

Reputation: 758

Wouldn't

(int) Math.Min(Int32.MaxValue, longValue)

be the correct way, mathematically speaking?

Upvotes: 5

Mashake
Mashake

Reputation: 121

The safe and fastest way is to use Bit Masking before cast...

int MyInt = (int) ( MyLong & 0xFFFFFFFF )

The Bit Mask ( 0xFFFFFFFF ) value will depend on the size of Int because Int size is dependent on machine.

Upvotes: 12

realbart
realbart

Reputation: 3964

Sometimes you're not actually interested in the actual value, but in its usage as checksum/hashcode. In this case, the built-in method GetHashCode() is a good choice:

int checkSumAsInt32 = checkSumAsIn64.GetHashCode();

Upvotes: 18

Mehrdad Afshari
Mehrdad Afshari

Reputation: 421998

Just do (int)myLongValue. It'll do exactly what you want (discarding MSBs and taking LSBs) in unchecked context (which is the compiler default). It'll throw OverflowException in checked context if the value doesn't fit in an int:

int myIntValue = unchecked((int)myLongValue);

Upvotes: 262

Max Schmeling
Max Schmeling

Reputation: 12509

Convert.ToInt32(myValue);

Though I don't know what it will do when it's greater than int.MaxValue.

Upvotes: 46

Related Questions