"Conversion failed when converting the nvarchar value 'department_id' to data type int."

Question

1.00/5 (1 vote)

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SQL-Server-2008R2

VB

Dim da As New SqlDataAdapter("SELECT Subjects.subject_name FROM Subjects " _
     & "INNER JOIN Departments_Subjects_junction ON Subjects.subject_id = Departments_Subjects_junction.subject_id " _
     & "INNER JOIN Semesters_Subjects_junction ON Subjects.subject_id = Semesters_Subjects_junction.subject_id " _
     & "WHERE Departments_Subjects_junction.department_id = @DepartmentID AND Semesters_Subjects_junction.semester_id = @SemesterID ", con)
       da.SelectCommand.Parameters.AddWithValue("@DepartmentID", departmentCb.ValueMember)
       da.SelectCommand.Parameters.AddWithValue("@SemesterID", semesterCb.ValueMember)
       da.Fill(dt)
       con.Close()
       If dt.Rows.Count = 0 Then
           MessageBox.Show("No record exists, try again", "SORRY!", MessageBoxButtons.OK)
       End If

Posted 27-Oct-15 3:36am

hlsc1983

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Duncan Edwards Jones · Answer 1 · 2015-10-27T03:54:00

Solution 1

"ValueMember"[^] (for a combo box) returns the name of the property that provides the value - not the actual value itself.

I suspect that you meant to have departmentCB.SelectedValue [^]?

Posted 27-Oct-15 3:54am

Duncan Edwards Jones

Comments

Zoltán Zörgő 27-Oct-15 13:18pm

Looks a good catch! +5

Sergey Alexandrovich Kryukov · Answer 2 · 2015-10-27T03:55:00

No wonder; nothing guarantees you that some random string value always holds correct representation of an integer value.
The whole idea put in your database schema is wrong. You either need to make your department_id a string uniquely identifying your department in required scope, not limiting it to integers, or use proper data type representing a numeric value. Anyway, you should never use string types where numeric data is required; it's both inefficient and unreliable.

See, for example, https://msdn.microsoft.com/en-us/library/ms187745.aspx[^].

—SA

hlsc1983 · Answer 3 · 2015-10-27T06:01:00

Solution 3

SQL

da.SelectCommand.Parameters.AddWithValue("@DepartmentID", departmentCb.SelectedValue)
       da.SelectCommand.Parameters.AddWithValue("@SemesterID", semesterCb.SelectedValue)

Posted 27-Oct-15 6:01am