ulong keyword is used in field, method, property, and variable declarations and in cast and
typeof operations as an alias for the .NET Framework structure
System.UInt64. That is, it represents a 64-bit unsigned integer whose value ranges from 0 to 18,446,744,073,709,551,615.
|Special C# Identifiers (Contextual Keywords)|
|Contextual Keywords (Used in Queries)|