Querying database (SQL Server) from Microsoft Visual Studio

Question

Beginner level programmer here and I've been stuck with this issue of querying my database (SQL Server) through Microsoft Visual Studio and actually returning the tuple of the result I want.

For instance.. If I want the sector of a particular Project ID, I'd query it like this in a subroutine, and call the subroutine

Public Sub testing()
    projectID = 1

    Dim sqlQueryObject = (From a In db.Project1 Where a.ProjectID = projectID
                          Select a.Sector)   'Using LINQ

    'Now have the object (works fine)
    'The Issue is getting the actual sector value from this query...in which I've tried a couple of things

End Sub

1. dim somestring as string = Cstr(sqlQueryObject)
2. dim somestring as string = Ctype(sqlqueryobject, string)

Neither work, If the sector for projectID 1 is named Zero - How do I program it to return this value?

Answer 1

The LINQ query you have given will return a list containing the elements that meet the criteria in your Where clause. For the query to only return a single value you need to apply either .Single(), .SingleOrDefault(), .First() or .FirstOrDefault() to the query.

For example the following would return either a single scalar value or the default value of the type being returned.

Dim sector = (From a In db.Project1 
              Where a.ProjectID = projectID
              Select a.Sector
             ).SingleOrDefault() 

Further information about these methods can be found in this question.