I am using a Strongly Typed Dataset
as DAL.
I want to return a single column from my table for that i wrote the code as
SELECT DISTINCT Floor
FROM Room
WHERE (Building = @Building)
But when i previewed the data, it shows me all the columns of the table with Null Value and the column with primary key has -1 value.
This condition raise an Exception when i link this query to a ComboBox ..
cmbFloor.DataSource = da.GetFloorByBuilding(cmbBuilding.Text)
cmbFloor.DisplayMember = "Floor"
Error:
Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
Since each table in Strongly Typed Dataset is stored as a Class. When a query returns a table value or any scalar value. The Dataset returns an class object which contains all properties.