User-556137015 posted
Hi guys,
I have the following problem, I am trying to do a simple 3 tier application to grasp the logic. I have a data access layer and a business logic layer, and my presentation layer just has 1 dropdownlist.
I want the dropdownlist to load and when I click on a item, it must return the ides, Now i know how to do that (selected_index_changed). I can not seem to load information to my dropdownlist. I am using a simple stored procedure (select *
from test). I will paste the code from the different layers and also the error. How can I solve this error.
Data Access Layer :-
Imports System
Imports System.Collections.Generic
Imports System.Data
Imports System.Linq
Imports System.Text
Imports System.Data.SqlClient
Imports System.Configuration
Public Class csSQLDALVB
Protected _strconn As String = ConfigurationManager.ConnectionStrings("MyConn").ConnectionString
Private conn As SqlConnection
Private errorstr As String = String.Empty
'default method
Public Sub New()
conn = New SqlConnection()
End Sub
'gets and sets the connection string
Public Property ConnectionString() As String
Get
Return _strconn
End Get
Set(ByVal value As String)
_strconn = value
End Set
End Property
'this is to get a open open connection to our database
Private Function Open_Connection() As Boolean
If conn.State = System.Data.ConnectionState.Closed Then
Try
conn.ConnectionString = ConnectionString
conn.Open()
Return True
Catch a As Exception
errorstr += " " & a.Message
Return False
End Try
Else
Return True
End If
End Function
'this is for our parameters for our queries
Private Function add_parameters(ByVal objpar As csParameterListType) As SqlParameter
Dim sqlpar As New SqlParameter()
sqlpar.ParameterName = objpar.Name
sqlpar.SqlDbType = objpar.SqlType
sqlpar.SqlValue = objpar.Value
Return sqlpar
End Function
'This can loop and read through all the records from the table
Public Function executespreturndr(ByVal spname As String, ByVal objlist As List(Of csParameterListType)) As IDataReader
Dim cmd As New SqlCommand()
Dim dr As IDataReader = Nothing
Try
If Open_Connection() Then
cmd.Connection = conn
cmd.CommandType = System.Data.CommandType.StoredProcedure
cmd.CommandText = spname
For Each par As csParameterListType In objlist
cmd.Parameters.Add(add_parameters(par))
Next
dr = cmd.ExecuteReader(CommandBehavior.CloseConnection)
End If
Return dr
Catch e As Exception
errorstr += " " & e.Message
Return Nothing
End Try
End Function
'this can be used for just executing a stored procedure for example "GET 10 BEST SELLING"
Public Function executespreturndr(ByVal spname As String) As IDataReader
Dim cmd As New SqlCommand()
Dim dr As IDataReader = Nothing
Try
If Open_Connection() Then
cmd.Connection = conn
cmd.CommandType = System.Data.CommandType.StoredProcedure
cmd.CommandText = spname
dr = cmd.ExecuteReader(CommandBehavior.CloseConnection)
End If
Return dr
Catch e As Exception
errorstr += " " & e.Message
Return Nothing
End Try
End Function
'this can insert into the database
Public Sub executespreturnnd(ByVal spname As String, ByVal objlist As List(Of csParameterListType))
Dim cmd As New SqlCommand()
Try
If Open_Connection() Then
cmd.Connection = conn
cmd.CommandType = System.Data.CommandType.StoredProcedure
cmd.CommandText = spname
For Each par As csParameterListType In objlist
cmd.Parameters.Add(add_parameters(par))
Next
cmd.ExecuteNonQuery()
close_conn()
End If
Catch e As Exception
errorstr += " " & e.Message
End Try
End Sub
'this inserts the record and returns the ID of the inserted record
Public Function executespreturnID(ByVal spname As String, ByVal objlist As List(Of csParameterListType))
Dim cmd As New SqlCommand()
Dim ID As Integer
Try
If Open_Connection() Then
cmd.Connection = conn
cmd.CommandType = System.Data.CommandType.StoredProcedure
cmd.CommandText = spname
For Each par As csParameterListType In objlist
cmd.Parameters.Add(add_parameters(par))
Next
ID = cmd.ExecuteScalar()
close_conn()
End If
Catch e As Exception
errorstr += " " & e.Message
End Try
Return ID
End Function
'this closes the db connection
Private Sub close_conn()
If conn.State = System.Data.ConnectionState.Open Then
conn.Close()
End If
conn = Nothing
End Sub
End Class
Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Data
Public Class csParameterListType
Private _Name As String
Public Property Name() As String
Get
Return _Name
End Get
Set(ByVal value As String)
_Name = value
End Set
End Property
Private _SqlType As SqlDbType
Public Property SqlType() As SqlDbType
Get
Return _SqlType
End Get
Set(ByVal value As SqlDbType)
_SqlType = value
End Set
End Property
Private _Value As String
Public Property Value() As String
Get
Return _Value
End Get
Set(ByVal value As String)
_Value = value
End Set
End Property
Public Sub New(ByVal name__1 As String, ByVal Stype As SqlDbType, ByVal value__2 As String)
Name = name__1
SqlType = Stype
Value = value__2
End Sub
End Class
Business Logic Layer
Imports DataAccessLayer
Public Class DropDownList
Private _IDn As Integer
Private _Name, _Surname As String
Public Sub New()
End Sub
Public Sub New(ByVal N As String, ByVal S As String, ByVal IDn As Integer)
propName = N
propSurname = S
propID = IDn
End Sub
Public Property propName() As String
Get
Return _Name
End Get
Set(ByVal value As String)
_Name = value
End Set
End Property
Public Property propSurname() As String
Get
Return _Surname
End Get
Set(ByVal value As String)
_Surname = value
End Set
End Property
Public Property propID() As Integer
Get
Return _IDn
End Get
Set(ByVal value As Integer)
_IDn = value
End Set
End Property
Public Function Get_All_Names() As List(Of DropDownList)
Dim objDal As New csSQLDALVB
Dim objListpb As New List(Of DropDownList)
Dim dr As System.Data.IDataReader
dr = objDal.executespreturndr("sp_get_all")
Using dr
While dr.Read
Dim objpb As New DropDownList
Populate_data(dr, objpb)
objListpb.Add(objpb)
End While
End Using
Return objListpb
End Function
Private Sub Populate_data(ByVal objread As System.Data.IDataReader, ByVal objt As DropDownList)
objt.propID = objread.GetInt32(0)
objt.propName = objread.GetString(1)
objt.propSurname = objread.GetString(2)
End Sub
End Class
Presentation Layer
Imports BusinessLogic
Partial Public Class DropDownList
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not Page.IsPostBack Then
LoadInfo()
End If
End Sub
Public Sub LoadInfo()
Dim obj As New BusinessLogic.DropDownList
DropDownList1.DataSource = obj.Get_All_Names
DropDownList1.DataTextField = obj.propName
DropDownList1.DataValueField = obj.propID
DropDownList1.DataBind()
End Sub
End Class
Error
Server Error in '/' Application.
DataBinding: 'BusinessLogic.DropDownList' does not contain a property with the name '0'.
Description:
An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Web.HttpException: DataBinding: 'BusinessLogic.DropDownList' does not contain a property with the name '0'.
Source Error:
Line 19: DropDownList1.DataTextField = obj.propName
Line 20: DropDownList1.DataValueField = obj.propID
Line 21: DropDownList1.DataBind()
Line 22:
Line 23:
|
Source File: C:\Users\KRATOS\Documents\Visual Studio 2008\Projects\Example\PresentationLayer\DropDownList.aspx.vb Line:
21
Stack Trace:
[HttpException (0x80004005): DataBinding: 'BusinessLogic.DropDownList' does not contain a property with the name '0'.]
System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName) +8661733
System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName, String format) +8
System.Web.UI.WebControls.ListControl.PerformDataBinding(IEnumerable dataSource) +381
System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e) +107
System.Web.UI.WebControls.ListControl.PerformSelect() +34
System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +73
PresentationLayer.DropDownList.LoadInfo() in C:\Users\KRATOS\Documents\Visual Studio 2008\Projects\Example\PresentationLayer\DropDownList.aspx.vb:21
PresentationLayer.DropDownList.Page_Load(Object sender, EventArgs e) in C:\Users\KRATOS\Documents\Visual Studio 2008\Projects\Example\PresentationLayer\DropDownList.aspx.vb:9
System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +50
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627
|
Version Information: Microsoft .NET Framework Version:2.0.50727.4927; ASP.NET Version:2.0.50727.4927
<!-- [HttpException]: DataBinding: 'BusinessLogic.DropDownList' does not contain a property with the name '0'. at System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName) at System.Web.UI.DataBinder.GetPropertyValue(Object container,
String propName, String format) at System.Web.UI.WebControls.ListControl.PerformDataBinding(IEnumerable dataSource) at System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e) at System.Web.UI.WebControls.ListControl.PerformSelect() at System.Web.UI.WebControls.BaseDataBoundControl.DataBind()
at PresentationLayer.DropDownList.LoadInfo() in C:\Users\KRATOS\Documents\Visual Studio 2008\Projects\Example\PresentationLayer\DropDownList.aspx.vb:line 21 at PresentationLayer.DropDownList.Page_Load(Object sender, EventArgs e) in C:\Users\KRATOS\Documents\Visual
Studio 2008\Projects\Example\PresentationLayer\DropDownList.aspx.vb:line 9 at System.Web.UI.Control.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
[HttpUnhandledException]: Exception of type 'System.Web.HttpUnhandledException' was thrown. at System.Web.UI.Page.HandleError(Exception e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) at System.Web.UI.Page.ProcessRequest(HttpContext
context) at ASP.dropdownlist_aspx.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
-->
