Visual Basic HowTo：从.mdf检索数据

Question

我在做什么错？我一直在这一段时间......我投降了。

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 
     Using sqlCon = New SqlConnection("Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\gadgetDatabase.mdf;Integrated Security=True") 

     Dim Id As Integer = 2 
     'With the use of ID, it will get the appName or Application Display Name 
     sqlCon.Open() 
     Dim sqlText = "SELECT appName " & _ 
         "FROM appTable " & _ 
         "WHERE Id = @sqlID" 
     Dim sqlCmd = New SqlCommand(sqlText, sqlCon) 
     sqlCmd.Parameters.AddWithValue("@sqlID", Id) 
     'sqlCmd.ToString() 
     sqlCmd.ExecuteScalar() 'I had these in there before I copied the code over 
     sqlCon.Close() 
     Label3.Text = sqlText 'For testing or confirmation it went correctly... 

    End Using 

End Sub 

Answer 1

你忘了打电话给

string apName = sqlCmd.ExecuteScaler(); 

并检索结果。

如果预期结果集（多个结果），则调用reader = cmd.ExecuteReader()并遍历结果。