When submitting, simply construct a hashtable of U-SQL variable names to values and pass it in using the -ScriptParameter cmdlet parameter. The .NET type of each value in the hashtable is used when defining the variable in U-SQL.
Supported types include:
byte, sbyte, int, uint (or uint32), long, ulong (or uint64), float, double, decimal, short (or int16), ushort (or uint16), char, string, DateTime, bool, Guid, or byte
Read on for an example of the process.