Convert.ToUInt64 Method in C#

The Convert.ToUInt64() method in C# converts a specified value to a 64-bit unsigned integer (ulong). This method accepts various data types and returns their equivalent ulong representation.

Syntax

Following is the syntax for the Convert.ToUInt64() method −

public static ulong ToUInt64(object value)
public static ulong ToUInt64(string value)
public static ulong ToUInt64(char value)
public static ulong ToUInt64(int value)
public static ulong ToUInt64(double value)

Parameters

• value − The value to convert. Can be of type object, string, char, numeric types, or other convertible types.

Return Value

Returns a 64-bit unsigned integer (ulong) equivalent to the specified value. If the value is null, the method returns 0.

Using Convert.ToUInt64() with Different Data Types

Converting Character to UInt64

When converting a character, the method returns the ASCII value of that character −

using System;

public class Demo {
    public static void Main() {
        char ch = 'a';
        ulong res = Convert.ToUInt64(ch);
        Console.WriteLine("Converted char value '{0}' to {1}", ch, res);
        
        char ch2 = 'Z';
        ulong res2 = Convert.ToUInt64(ch2);
        Console.WriteLine("Converted char value '{0}' to {1}", ch2, res2);
    }
}

The output of the above code is −

Converted char value 'a' to 97
Converted char value 'Z' to 90

Converting String to UInt64

The method can parse numeric strings and convert them to ulong values −

using System;

public class Demo {
    public static void Main() {
        string str1 = "12345";
        string str2 = "18446744073709551615"; // Maximum ulong value
        
        ulong result1 = Convert.ToUInt64(str1);
        ulong result2 = Convert.ToUInt64(str2);
        
        Console.WriteLine("String '{0}' converted to: {1}", str1, result1);
        Console.WriteLine("String '{0}' converted to: {1}", str2, result2);
    }
}

The output of the above code is −

String '12345' converted to: 12345
String '18446744073709551615' converted to: 18446744073709551615

Converting Different Numeric Types

The method works with various numeric data types −

using System;

public class Demo {
    public static void Main() {
        int intValue = 100;
        double doubleValue = 123.45;
        decimal decimalValue = 999.99m;
        
        ulong fromInt = Convert.ToUInt64(intValue);
        ulong fromDouble = Convert.ToUInt64(doubleValue);
        ulong fromDecimal = Convert.ToUInt64(decimalValue);
        
        Console.WriteLine("int {0} to ulong: {1}", intValue, fromInt);
        Console.WriteLine("double {0} to ulong: {1}", doubleValue, fromDouble);
        Console.WriteLine("decimal {0} to ulong: {1}", decimalValue, fromDecimal);
    }
}

The output of the above code is −

int 100 to ulong: 100
double 123.45 to ulong: 123
decimal 999.99 to ulong: 999

Key Rules

• The method rounds floating-point values to the nearest integer.

• Negative values will throw an OverflowException since ulong is unsigned.

• Values exceeding the ulong range (0 to 18,446,744,073,709,551,615) will throw an OverflowException.

• If the input string cannot be parsed, a FormatException is thrown.

Conclusion

The Convert.ToUInt64() method provides a convenient way to convert various data types to 64-bit unsigned integers. It handles characters by returning their ASCII values, parses numeric strings, and converts other numeric types while applying appropriate rounding for floating-point values.