Why am I getting an object reference not set error?

I can't seem to figure out why the below code is giving me the following error:

Object reference not set to an instance of an object.
Line 47:             objSQLCommand.Connection.Open()

This is the problem code:

Function getTabContent() As String
    Dim strUserInitials() As String = Request.ServerVariables("LOGON_USER").Split(CChar("\"))
    strUser = LCase(Trim(strUserInitials(strUserInitials.GetUpperBound(0)))).ToString()

    objStringBuilder = New StringBuilder()

    For intColumn As Integer = 1 To 3
        objSQLCommand = New SqlCommand("select c.*, w.* " & _
        "from intranet.dbo.tabs t " & _
        "inner join intranet.dbo.columns c on t.id = c.tabs_id " & _
        "inner join intranet.dbo.widgets w on c.widgets_id = w.widget_id " & _
        "where t.is_default = 0 " & _
        "and t.cms_initials = @user " & _
        "and t.id = @tab " & _
        "and c.sort_column = @column " & _
        "and w.inactive = 0 " & _
        "order by c.tabs_id, c.sort_column, c.sort_row", objSQLConnection)

        objSQLCommand.Parameters.Add("@user", SqlDbType.VarChar, 3).Value = strUser
        objSQLCommand.Parameters.Add("@tab", SqlDbType.Int, 4).Value = Request.QueryString("tab")
        objSQLCommand.Parameters.Add("@column", SqlDbType.Int, 4).Value = intColumn

        objStringBuilder.Append("<div class=""column"" id=""column_" & intColumn & """>")

        objSQLCommand.Connection.Open()
        objSQLDataReader = objSQLCommand.ExecuteReader()

        While obj开发者_如何学PythonSQLDataReader.Read()
            objStringBuilder.Append("<div class=""portlet"" id=""portlet_" & objSQLDataReader("widget_id") & """>")
            objStringBuilder.Append("<div class=""portlet-header"">" & objSQLDataReader("widget_name") & "</div>")
            objStringBuilder.Append("<div class=""portlet-content"">" & objSQLDataReader("widget_description") & "</div>")
            objStringBuilder.Append("</div>")
        End While

        objSQLDataReader.Close()
        objSQLCommand.Connection.Close()

        objStringBuilder.Append("</div>")
    Next intColumn

    Return objStringBuilder.ToString
End Function

---

The problem appears to be that the Connection property on objSqlCommand is Nothing and hence you get a NullReferenceException when you access it. This means in all likely hood that objSqlConnection is also Nothing and that is likely the root cause of your problem.

---

Connection is an object of type SqlConnection. You need to create an instance of this object before you can interact with it. Something like this:

Dim connection As New SqlConnection("your_connection_string")
objSQLCommand.Connection = connection
objSQLCommand.Connection.Open()
objSQLDataReader = objSQLCommand.ExecuteReader()

---

Instead of doing this

  objSQLCommand.Connection.Open()
        objSQLDataReader = objSQLCommand.ExecuteReader()

        While objSQLDataReader.Read()
            objStringBuilder.Append("<div class=""portlet"" id=""portlet_" & objSQLDataReader("widget_id") & """>")
            objStringBuilder.Append("<div class=""portlet-header"">" & objSQLDataReader("widget_name") & "</div>")
            objStringBuilder.Append("<div class=""portlet-content"">" & objSQLDataReader("widget_description") & "</div>")
            objStringBuilder.Append("</div>")
        End While

        objSQLDataReader.Close()
        objSQLCommand.Connection.Close()

just do

 objSQLConnection.Open()
        objSQLDataReader = objSQLCommand.ExecuteReader()

        While objSQLDataReader.Read()
            objStringBuilder.Append("<div class=""portlet"" id=""portlet_" & objSQLDataReader("widget_id") & """>")
            objStringBuilder.Append("<div class=""portlet-header"">" & objSQLDataReader("widget_name") & "</div>")
            objStringBuilder.Append("<div class=""portlet-content"">" & objSQLDataReader("widget_description") & "</div>")
            objStringBuilder.Append("</div>")
        End While


        objSQLConnection.Close()