Gets a value that indicates whether this System.Globalization.NumberFormatInfo object is read-only.
true if the current instance is read-only; otherwise false.
Attempting to perform an assignment to a property of a read-only System.Globalization.NumberFormatInfo causes an InvalidOperationException.
You can call the NumberFormatInfo.Clone method to create a read/write System.Globalization.NumberFormatInfo object from a read-only object, as the following example illustrates.
code reference: System.Globalization.NumberFormatInfo.IsReadOnly#1