Decimal.ToUInt64() Method in C#

The Decimal.ToUInt64() method in C# converts a decimal value to a 64-bit unsigned integer (ulong). This method performs truncation, meaning it removes the fractional part and returns only the integer portion of the decimal number.

Syntax

Following is the syntax −

public static ulong ToUInt64(decimal value);

Parameters

• value − The decimal number to convert to a 64-bit unsigned integer.

Return Value

Returns a ulong (64-bit unsigned integer) that represents the truncated value of the specified decimal.

Using Decimal.ToUInt64() with Fractional Values

When the decimal has a fractional part, the method truncates it and returns only the integer portion −

using System;

public class Demo {
   public static void Main() {
      Decimal val = 99.29m;
      Console.WriteLine("Decimal value = " + val);
      ulong res = Decimal.ToUInt64(val);
      Console.WriteLine("64-bit unsigned integer = " + res);
   }
}

The output of the above code is −

Decimal value = 99.29
64-bit unsigned integer = 99

Using Decimal.ToUInt64() with Small Decimal Values

When the decimal value is less than 1, the method returns 0 since the integer part is 0 −

using System;

public class Demo {
   public static void Main() {
      Decimal val = 0.001m;
      Console.WriteLine("Decimal value = " + val);
      ulong res = Decimal.ToUInt64(val);
      Console.WriteLine("64-bit unsigned integer = " + res);
   }
}

The output of the above code is −

Decimal value = 0.001
64-bit unsigned integer = 0

Using Decimal.ToUInt64() with Large Values

The method can handle large decimal values within the ulong range −

using System;

public class Demo {
   public static void Main() {
      Decimal val1 = 1000000.99m;
      Decimal val2 = 18446744073709551615m; // Max ulong value
      
      Console.WriteLine("Decimal value 1 = " + val1);
      Console.WriteLine("Converted to UInt64 = " + Decimal.ToUInt64(val1));
      
      Console.WriteLine("Decimal value 2 = " + val2);
      Console.WriteLine("Converted to UInt64 = " + Decimal.ToUInt64(val2));
   }
}

The output of the above code is −

Decimal value 1 = 1000000.99
Converted to UInt64 = 1000000
Decimal value 2 = 18446744073709551615
Converted to UInt64 = 18446744073709551615

Exception Handling

The method throws an OverflowException if the decimal value is negative or exceeds the maximum value of ulong −

using System;

public class Demo {
   public static void Main() {
      try {
         Decimal negativeVal = -10.5m;
         Console.WriteLine("Attempting to convert: " + negativeVal);
         ulong result = Decimal.ToUInt64(negativeVal);
      }
      catch (OverflowException ex) {
         Console.WriteLine("OverflowException: " + ex.Message);
      }
   }
}

The output of the above code is −

Attempting to convert: -10.5
OverflowException: Value was either too large or too small for a UInt64.

Conclusion

The Decimal.ToUInt64() method converts decimal values to 64-bit unsigned integers by truncating the fractional part. It throws an OverflowException for negative values or values exceeding the ulong range, making it essential to handle potential exceptions in real-world applications.