Yes

But you should know that setting the field as readonly doesnt mean that
the values of the array cannot be altered. The following code will
change the value of the element at index 2:

GrageLookupTable[2] = "Test";

To make it truly readonly, make the field a property and return a clone
of the array so that no one can change the original values of the
array:

public static Grades {
get {return GradeLookupTable.Clone() as string[];}
}

- NuTcAsE