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()