E
egi
Hi!
Please help me to solve this problem. I have a dropdownlist on a page, which
is populated trough database (databind).
Page is working well till form submit. When i submit a page and try to get
value of dropdown, i get this error:
******************* ERROR ********************
Object reference not set to an instance of an object.
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.NullReferenceException: Object reference not set
to an instance of an object.
Source Error:
Line 103: lblError.Visible = True
Line 104: btnSubmit.Visible = False
Line 105: lblError.Text = request_department.SelectedItem.Value
Line 106:
Line 107: 'lblError.Text = request_informer_email.Text.ToString &
"<br><br>" & _
***************************************************
***************************************************
Code Behind:
***************************************************
Public Class AddRequest
Inherits System.Web.UI.UserControl
#Region " Web Form Designer Generated Code "
'This call is required by the Web Form Designer.
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
End Sub
Protected WithEvents tblRequest As System.Web.UI.WebControls.Table
Protected WithEvents tblInformer As System.Web.UI.WebControls.Table
Protected WithEvents request_department As
System.Web.UI.WebControls.DropDownList
Protected WithEvents request_name As System.Web.UI.WebControls.TextBox
Protected WithEvents request_text As System.Web.UI.WebControls.TextBox
Protected WithEvents request_informer As System.Web.UI.WebControls.TextBox
Protected WithEvents request_informer_email As
System.Web.UI.WebControls.TextBox
Protected WithEvents request_informer_phone As
System.Web.UI.WebControls.TextBox
Protected WithEvents request_informer_notify As
System.Web.UI.WebControls.CheckBox
Protected WithEvents lblError As System.Web.UI.WebControls.Label
Protected WithEvents btnSubmit As System.Web.UI.WebControls.Button
'NOTE: The following placeholder declaration is required by the Web Form
Designer.
'Do not delete or move it.
Private designerPlaceholderDeclaration As System.Object
Private Sub Page_Init(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Init
'CODEGEN: This method call is required by the Web Form Designer
'Do not modify it using the code editor.
InitializeComponent()
End Sub
#End Region
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
'hide error label and main table
lblError.Visible = False
tblRequest.Visible = False
'check if page is not post back
If Not Page.IsPostBack Then
'show form on the page
ShowForm()
End If
End Sub
Private Sub ShowForm()
'show table
tblRequest.Visible = True
'declare SQL string
Dim sSQL As String
'initialize database class
Dim fConnectDB As connectDB = New connectDB
'declare datatable, datarow and dataview
Dim dtTable As DataTable
Dim drData As DataRow
Dim dvData As DataView
Try
'SQL string
sSQL = "EXEC sp_show_departments"
'connect to database and execute stored procedure sp_show_departments
fConnectDB.FillDataAdapter(sSQL, "Departments", "HelpDesk")
'get the dataset from database and add new row to it (default selection for
DropDown)
dtTable = fConnectDB.ReturnDataSet.Tables(0)
drData = dtTable.NewRow()
drData("department_name") = "--- Select department ---"
drData("id") = "0"
dtTable.Rows.Add(drData)
'sort data on field department_name
dvData = dtTable.DefaultView
dvData.Sort = "department_name"
'databind Dropdown list
request_department.DataSource = dvData.Table
request_department.DataTextField = "department_name"
request_department.DataValueField = "id"
request_department.DataBind()
'set default selection
request_department.SelectedValue = "0"
Catch ex As Exception
'catch posibble errors
tblRequest.Visible = False
lblError.Visible = True
lblError.Text = ex.ToString
End Try
End Sub
Sub btnSubmit_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnSubmit.Click
lblError.Visible = True
btnSubmit.Visible = False
lblError.Text = request_department.SelectedItem.Value '********** ERROR IS
HERE !!! *************
'*********** THIS IS WORKING OK !!! ****************
'lblError.Text = request_informer_email.Text.ToString & "<br><br>" & _
' request_informer.Text.ToString & "<br><br>" & _
' request_informer_phone.Text.ToString & "<br><br>" & _
' request_name.Text.ToString & "<br><br>" & _
' request_text.Text.ToString & "<br><br>"
End Sub
End Class
***************************************************
Page:
***************************************************
<%@ Control Language="vb" AutoEventWireup="false"
Codebehind="AddRequest.ascx.vb" Inherits="HelpDesk.AddRequest"
TargetSchema="http://schemas.microsoft.com/intellisense/ie5" %>
<asp:table id="tblRequest" EnableViewState="False" CellPadding="4"
CellSpacing="2" runat="server"
Width="100%" BorderStyle="None">
<asp:TableRow>
<asp:TableCell>
<b>Name:</b>
<asp:RequiredFieldValidator id="rfvName" ControlToValidate="request_name"
EnableViewState="False" runat="server"
ErrorMessage="Enter request name!"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ControlToValidate="request_name"
ValidationExpression=".{10,80}" Text="Min 10 and Max 80 characters!"
runat="server" ID="regexName"></asp:RegularExpressionValidator>
<br />
<asp:TextBox Runat="server" ID="request_name" MaxLength="80"
Width="100%"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>
<b>Description:</b>
<asp:RequiredFieldValidator id="rfvText" ControlToValidate="request_text"
EnableViewState="False" runat="server"
ErrorMessage="Enter request description!"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ControlToValidate="request_text"
ValidationExpression=".{10,1000}" Text="Min 10 and Max 1000 characters!"
runat="server" ID="regexDescription"></asp:RegularExpressionValidator>
<br />
<asp:TextBox Runat="server" ID="request_text" MaxLength="1000"
Width="100%" Rows="10" TextMode="MultiLine"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>
<b>Informer data:</b><br />
<asp:Table ID="tblInformer" Runat="server" CellPadding="0"
CellSpacing="2" EnableViewState="False"
BorderStyle="None" Width="100%">
<asp:TableRow>
<asp:TableCell>Full name:
<asp:RequiredFieldValidator id="rfvInformer"
ControlToValidate="request_informer" EnableViewState="False" runat="server"
ErrorMessage="Enter your full name!"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ControlToValidate="request_informer"
ValidationExpression=".{3,30}" Text="Min 3 and Max 30 characters!"
runat="server" ID="regexInformer"></asp:RegularExpressionValidator>
<br />
<asp:TextBox ID="request_informer" MaxLength="30" Width="200px"
Runat="server"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>Email:<br />
<asp:TextBox ID="request_informer_email" MaxLength="50" Width="200px"
Runat="server"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>Phone:<br />
<asp:TextBox ID="request_informer_phone" MaxLength="15" Width="110px"
Runat="server"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>Department:
<asp:RequiredFieldValidator id="rfvDepartment"
ControlToValidate="request_department" EnableViewState="False"
runat="server" InitialValue="0" ErrorMessage="Select
department!"></asp:RequiredFieldValidator><br />
<asp
ropDownList ID="request_department"
Runat="server"></aspropDownList> ******** DROP DOWN *********
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell ColumnSpan="2">
<br />
<asp:CheckBox ID="request_informer_notify" Runat="server" Text="Notify
me on changes"></asp:CheckBox>
</asp:TableCell>
</asp:TableRow>
</asp:Table>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>
<asp:button id="btnSubmit" text="Submit" onClick="btnSubmit_Click"
runat="server"></asp:button>
</asp:TableCell>
</asp:TableRow>
</asp:table>
<P><asp:label id="lblError" runat="server"
Visible="False">Error</asp:label></P>
Please help me to solve this problem. I have a dropdownlist on a page, which
is populated trough database (databind).
Page is working well till form submit. When i submit a page and try to get
value of dropdown, i get this error:
******************* ERROR ********************
Object reference not set to an instance of an object.
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.NullReferenceException: Object reference not set
to an instance of an object.
Source Error:
Line 103: lblError.Visible = True
Line 104: btnSubmit.Visible = False
Line 105: lblError.Text = request_department.SelectedItem.Value
Line 106:
Line 107: 'lblError.Text = request_informer_email.Text.ToString &
"<br><br>" & _
***************************************************
***************************************************
Code Behind:
***************************************************
Public Class AddRequest
Inherits System.Web.UI.UserControl
#Region " Web Form Designer Generated Code "
'This call is required by the Web Form Designer.
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
End Sub
Protected WithEvents tblRequest As System.Web.UI.WebControls.Table
Protected WithEvents tblInformer As System.Web.UI.WebControls.Table
Protected WithEvents request_department As
System.Web.UI.WebControls.DropDownList
Protected WithEvents request_name As System.Web.UI.WebControls.TextBox
Protected WithEvents request_text As System.Web.UI.WebControls.TextBox
Protected WithEvents request_informer As System.Web.UI.WebControls.TextBox
Protected WithEvents request_informer_email As
System.Web.UI.WebControls.TextBox
Protected WithEvents request_informer_phone As
System.Web.UI.WebControls.TextBox
Protected WithEvents request_informer_notify As
System.Web.UI.WebControls.CheckBox
Protected WithEvents lblError As System.Web.UI.WebControls.Label
Protected WithEvents btnSubmit As System.Web.UI.WebControls.Button
'NOTE: The following placeholder declaration is required by the Web Form
Designer.
'Do not delete or move it.
Private designerPlaceholderDeclaration As System.Object
Private Sub Page_Init(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Init
'CODEGEN: This method call is required by the Web Form Designer
'Do not modify it using the code editor.
InitializeComponent()
End Sub
#End Region
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
'hide error label and main table
lblError.Visible = False
tblRequest.Visible = False
'check if page is not post back
If Not Page.IsPostBack Then
'show form on the page
ShowForm()
End If
End Sub
Private Sub ShowForm()
'show table
tblRequest.Visible = True
'declare SQL string
Dim sSQL As String
'initialize database class
Dim fConnectDB As connectDB = New connectDB
'declare datatable, datarow and dataview
Dim dtTable As DataTable
Dim drData As DataRow
Dim dvData As DataView
Try
'SQL string
sSQL = "EXEC sp_show_departments"
'connect to database and execute stored procedure sp_show_departments
fConnectDB.FillDataAdapter(sSQL, "Departments", "HelpDesk")
'get the dataset from database and add new row to it (default selection for
DropDown)
dtTable = fConnectDB.ReturnDataSet.Tables(0)
drData = dtTable.NewRow()
drData("department_name") = "--- Select department ---"
drData("id") = "0"
dtTable.Rows.Add(drData)
'sort data on field department_name
dvData = dtTable.DefaultView
dvData.Sort = "department_name"
'databind Dropdown list
request_department.DataSource = dvData.Table
request_department.DataTextField = "department_name"
request_department.DataValueField = "id"
request_department.DataBind()
'set default selection
request_department.SelectedValue = "0"
Catch ex As Exception
'catch posibble errors
tblRequest.Visible = False
lblError.Visible = True
lblError.Text = ex.ToString
End Try
End Sub
Sub btnSubmit_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnSubmit.Click
lblError.Visible = True
btnSubmit.Visible = False
lblError.Text = request_department.SelectedItem.Value '********** ERROR IS
HERE !!! *************
'*********** THIS IS WORKING OK !!! ****************
'lblError.Text = request_informer_email.Text.ToString & "<br><br>" & _
' request_informer.Text.ToString & "<br><br>" & _
' request_informer_phone.Text.ToString & "<br><br>" & _
' request_name.Text.ToString & "<br><br>" & _
' request_text.Text.ToString & "<br><br>"
End Sub
End Class
***************************************************
Page:
***************************************************
<%@ Control Language="vb" AutoEventWireup="false"
Codebehind="AddRequest.ascx.vb" Inherits="HelpDesk.AddRequest"
TargetSchema="http://schemas.microsoft.com/intellisense/ie5" %>
<asp:table id="tblRequest" EnableViewState="False" CellPadding="4"
CellSpacing="2" runat="server"
Width="100%" BorderStyle="None">
<asp:TableRow>
<asp:TableCell>
<b>Name:</b>
<asp:RequiredFieldValidator id="rfvName" ControlToValidate="request_name"
EnableViewState="False" runat="server"
ErrorMessage="Enter request name!"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ControlToValidate="request_name"
ValidationExpression=".{10,80}" Text="Min 10 and Max 80 characters!"
runat="server" ID="regexName"></asp:RegularExpressionValidator>
<br />
<asp:TextBox Runat="server" ID="request_name" MaxLength="80"
Width="100%"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>
<b>Description:</b>
<asp:RequiredFieldValidator id="rfvText" ControlToValidate="request_text"
EnableViewState="False" runat="server"
ErrorMessage="Enter request description!"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ControlToValidate="request_text"
ValidationExpression=".{10,1000}" Text="Min 10 and Max 1000 characters!"
runat="server" ID="regexDescription"></asp:RegularExpressionValidator>
<br />
<asp:TextBox Runat="server" ID="request_text" MaxLength="1000"
Width="100%" Rows="10" TextMode="MultiLine"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>
<b>Informer data:</b><br />
<asp:Table ID="tblInformer" Runat="server" CellPadding="0"
CellSpacing="2" EnableViewState="False"
BorderStyle="None" Width="100%">
<asp:TableRow>
<asp:TableCell>Full name:
<asp:RequiredFieldValidator id="rfvInformer"
ControlToValidate="request_informer" EnableViewState="False" runat="server"
ErrorMessage="Enter your full name!"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ControlToValidate="request_informer"
ValidationExpression=".{3,30}" Text="Min 3 and Max 30 characters!"
runat="server" ID="regexInformer"></asp:RegularExpressionValidator>
<br />
<asp:TextBox ID="request_informer" MaxLength="30" Width="200px"
Runat="server"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>Email:<br />
<asp:TextBox ID="request_informer_email" MaxLength="50" Width="200px"
Runat="server"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>Phone:<br />
<asp:TextBox ID="request_informer_phone" MaxLength="15" Width="110px"
Runat="server"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>Department:
<asp:RequiredFieldValidator id="rfvDepartment"
ControlToValidate="request_department" EnableViewState="False"
runat="server" InitialValue="0" ErrorMessage="Select
department!"></asp:RequiredFieldValidator><br />
<asp
ropDownList ID="request_department"Runat="server"></asp
ropDownList> ******** DROP DOWN *********</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell ColumnSpan="2">
<br />
<asp:CheckBox ID="request_informer_notify" Runat="server" Text="Notify
me on changes"></asp:CheckBox>
</asp:TableCell>
</asp:TableRow>
</asp:Table>
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>
<asp:button id="btnSubmit" text="Submit" onClick="btnSubmit_Click"
runat="server"></asp:button>
</asp:TableCell>
</asp:TableRow>
</asp:table>
<P><asp:label id="lblError" runat="server"
Visible="False">Error</asp:label></P>