ULong Data Type (Visual Basic)

Holds unsigned 64-bit (8-byte) integers ranging in value from 0 through 18,446,744,073,709,551,615 (more than 1.84 times 10 ^ 19).

Remarks

Use the ULong data type to contain binary data too large for UInteger, or the largest possible unsigned integer values.

The default value of ULong is 0.

Negative Numbers. Because ULong is an unsigned type, it cannot represent a negative number. If you use the unary minus (-) operator on an expression that evaluates to type ULong, Visual Basic converts the expression to Decimal first.
CLS Compliance. The ULong data type is not part of the Language Independence and Language-Independent Components (CLS), so CLS-compliant code cannot consume a component that uses it.
Interop Considerations. If you are interfacing with components not written for the .NET Framework, for example Automation or COM objects, keep in mind that types such as ulong can have a different data width (32 bits) in other environments. If you are passing a 32-bit argument to such a component, declare it as UInteger instead of ULong in your managed Visual Basic code.

Furthermore, Automation does not support 64-bit integers on Windows 95, Windows 98, Windows ME, or Windows 2000. You cannot pass a Visual Basic ULong argument to an Automation component on these platforms.
Widening. The ULong data type widens to Decimal, Single, and Double. This means you can convert ULong to any of these types without encountering a System.OverflowException error.
Type Characters. Appending the literal type characters UL to a literal forces it to the ULong data type. ULong has no identifier type character.
Framework Type. The corresponding type in the .NET Framework is the System.UInt64 structure.