Parameter is missing a value ssrs 2008

Question

I have a parameter of integer datatype which is hidden. When i run the report, report gives me an error

Parameter X is missing a value

Answer 1

The problem occurs also, if you have a parameter that depends of another one without "default value" inside the Dataset Query and does not admit null value.

For example:

Parameter 1 have a default value: NameEmployee from the dataset "EmployeeSearch"

But the dataset "EmployeeSearch" have a filter or a parameter inside the query named @Month that indicate the number of the month. So if the value of @Month is null, SSRS will say "Parameter is missing a value".