Web Forms :: Accessing UserControl TextBox Null Reference?
Jan 20, 2011
I have a .ascx file residing in another page which has a button on it. On click I run a select statement that accesses the textbox for a value.
However, it keeps returning a Null Exception Error. I am trying access the textbox and its text through
[Code]....
I also tried -[Code]....
I also tried -[Code]....
But none of them work. Please can someone advise me how I find the textbox and then access its text?I have looked round the forums / google and cant find a way of doing this!
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Feb 16, 2010
I have a class that derives from System.Web.UI.Page and have set my pages to derive from this custom page class instead of Page. At runtime, the controls are never initialized and throw a NullReferenceException. I've changed some class names and namespaces in the pasted code to protect the innocent. The only thing that I currently override in my PageBase is OnPreLoad and I do call the base.OnPreLoad. I'll eventually add more functionality to this PageBase but for now all that it has is this:
[Code]....
I've tried putting this into a class library (with System.Web referenced) and I've also tried moving the class into the web application and had the same results either way. As another strange twist, I have another class with derives from PageBase called IndexPageBase and it doesn't have this problem:
[Code]....
[Code]....
[Code]....
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Jan 19, 2011
I have two UserControls on a MasterPage. DataEntryUC contains several TextBoxes and DropDownList. NavSaveUC contains navigation buttons. When the user clicks on a navigation button, I will be saving the data entered into DataEntryUC from the NavSaveUC UserControl.
I have a couple of tables in my DB that contain stored procedure names, control names, control types, SqlDbTypes, etc.... that correlate with DataEntryUC.
How do I reference a text box that is on DataEntryUC from NavSaveUC?
I have been working on the following code from NavSaveUC with no luck.
Dim MyControlName = "txtFirstName"
Dim MyControlType = "TextBox"
Dim MyStringValue as String
Dim tmpTxtControl as TextBox
Dim tmpDdlControl as DropDownList
Select Case MyControlType
Case "TextBox"
tmpTxtControl = CType(Page.FindControl(MyControlName, TextBox)
MyStringValue = tmpTxtControl.Text
Case "DropDownList"
tmpDdlControl = CType(Page.FindControl(MyControlName, DropDownList)
MyStringValue = tmpDdlControl.SelectedValue
End Select
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Apr 19, 2010
In the same Code behind file I have:
// This works
Label lblTopNavBarInfo = (Label)Master.FindControl("lblTopNavBarInfo");
lblTopNavBarInfo.Text = "Currently Serving: + FirstName + " " + LastName ;
// This compiles but throws an error in the browser
LinkButton lnkBtnProductsOwned = (LinkButton)LeftNav_CustServ1.FindControl("ProductsOwned"); // The Control is visible
lnkBtnProductsOwned.Enabled = false; // Error: Object reference not set to an instance of an object.
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Mar 11, 2011
accessing the currently edited existing row in the Radgrid, as as well as the index of the Edit form when trying to add a new record to the table/
function OnClientSelectedIndexChanged(sender, eventArgs) {
var item = eventArgs.get_item();
// alert(item.get_value());
grid = $find("<%= rgSecurity.ClientID %>");
[Code]....
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Oct 27, 2010
I have a GridView with the following columns
<asp:TemplateField HeaderText="Name">
<FooterTemplate>
<asp:TextBox ID="txt_Name" runat="server"></asp:TextBox>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lbl_name" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "t_Name") %>' />
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txt_name" runat="server" Width="100px" Text='<%#DataBinder.Eval(Container.DataItem,"t_Name") %>'></asp:TextBox>
</EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Created By">
<ItemTemplate>
<asp:Label ID="lbl_tabcreatedby" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "t_CreatedBy") %>' />
</ItemTemplate>
</asp:TemplateField>
<asp:CommandField HeaderText="Modify" ShowEditButton="True" />
<asp:CommandField HeaderText="Delete" ShowDeleteButton="True" />
<asp:TemplateField HeaderText="Add a New Name">
<FooterTemplate>
<asp:LinkButton ID="lnkbtn_AddName" runat="server" CommandName="Insert">Add Name</asp:LinkButton>
</FooterTemplate>
</asp:TemplateField>
And then in the Code Behind I am trying to access the txt_Name Textbox as
protected void gv_Name_RowCommand(object sender, GridViewCommandEventArgs e)
{
string t_Name = ((TextBox)(gv_Name.FooterRow.FindControl("txt_Name"))).Text;
// Insert Code
}
But I am getting null in the string t_Name everytime irrespective of what is the current Text of txt_Name.
However I can get the text if I disable the ViewState for the page.
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Feb 24, 2010
I am using dropdownlist in my view page with some values which will display corresponding ID(primary key of other table) in my database.If i leave my dropdownlist blank and save it in database then its showing null parameter error. Can you explain how to use this reference type to overcome this error
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Mar 24, 2010
I have a page which holds a custom webcontrol and a usercontrol. I need to reference of webcontrol in usercontrol class. So, I make the declaration of webcontrol as public in page class. But, when I do "this.Page.", I don't see the webcontrol listed in list provided by intellisense. Most probably, I am missing something.
In an asp.net page, how to get a reference of a custom webcontrol from a usercontrol?
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Apr 20, 2010
I am developing a usercontrol, in this case a toolbar. Some of the buttons on the toolbar will interact with other objects on the page which are not part of the toolbar. (In this case a map) So the toolbar code behind wants to say something like this:
[code]....
My problem is that MyMap does not exist in the design environment of the usercontrol and therefore produces an error when it is referenced. So my question is, How is this typically handled? Can the usercontrol reference another control that does not exist within itself?
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Mar 4, 2011
I have a usercontrol hosted on a page, registered through the web.config.
On the host page, I would like to programmatically reference the my public propeties of the user control in the codefile.
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Mar 23, 2010
I have a UserControl inside the ItemTemplate of my FormView and I need to access it in order to get an event fired off. As the UserControl is inside the template, my event cannot see it!
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Jun 1, 2010
I am having trouble trying to access a UserControl I created and placed inside the EditTemplate of the ListView. How is it done? I've tried to access it at the ListView's ItemDataBound, ItemEditing and Databound with the following code with no luck:
ucEditTask = DirectCast(lvTimeEntry.FindControl("ucEditTask"), UserControl)
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Feb 10, 2011
I am trying to use the already written code which accesses a control from an other control in the following code.
Controls_SearchFeaturedMerchants UCMerchant = (Controls_SearchFeaturedMerchants)this.Parent.FindControl("UCSearchFeaturedMerchants1");
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Sep 10, 2010
xamount is receiving this message on the last line. The session is being set in the previous page. Is there a way to resolve the message or should I just use a previous page postback
[Code]....
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Jan 6, 2011
I'm working on an ASP.NET app.I'm using a UserControl for a year calendar.This UserControl has 12 asp.net calendar controls (for the 12 months of a year)
I'm trying to build a jscript function that can access to one (or more) of the 12 month calendar, but I can't access them.
example:
"<asp:Calendar ID="CalendarJanuary" runat="server"></asp:Calendar>"
here's my function
function SetCalendar(controlId) {
document.getElementById(controlId+'_CalendarJanuary').VisibleDate = somedate
}
but this is allways throwing an error:'Microsoft JScript runtime error: 'document.getElementById(...)' is null or not an object'
it seems is not finding the calendar and I'm sure i'm passing the right controlID
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May 25, 2010
I have a custom component:
[Code]....
[Code]....
I try to create a new component instance like this:[Code]....
[Code]....
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May 28, 2010
I'm experimenting with validating forms in the asp.net MVC framework. I'm focusing on server side validation for the time being. I've come across an error that I'm not sure how to rectify. System.NullReferenceException: Object reference not set to an instance of an object. The code that throws the error is:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create([Bind(Exclude="ID")] MembersCreate mc )
{
mc.Modules = ModuleListDataContext.GetModuleList();
ViewData.Model = mc;
//Validation using ModelState
//
//
//line below errors when form field is empty
//
if ((string)mc.Member.Username.Trim() == "")
ModelState.AddModelError("Member.Username", "Username is required.");
if (!ModelState.IsValid)
return View();
try
{
// TODO: Add insert logic here
return RedirectToAction("Index","Home");
}
catch
{
return View();
}
}
When I put spaces in the field it performs exactly as i want, but if I leave the field blank and press submit I get the error. What's the best way to avoid this error and still validate blank form fields?
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Dec 10, 2010
I am getting the Null reference exception in
[Code]....
also when I used the Quickwatch, I get this error message.
getElementById The name 'getElementById' does not exist in the current context
I am also using Master Pages.
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Jul 9, 2012
This is my button event code
protected void ImageButton2_Click1(object sender, ImageClickEventArgs e)
{
string data = Server.UrlDecode(Request.QueryString["BehCode3"]);
string filename = System.IO.Path.GetFileName(fup1.PostedFile.FileName);
string filename1 = System.IO.Path.GetFileName(fup2.PostedFile.FileName);
string filename2 = System.IO.Path.GetFileName(fup3.PostedFile.FileName);
[Code]...
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Mar 10, 2010
I've got a master page where I've created two content place holders ('menu content place holder' and 'main body content place holder'). I've placed several controls (drop down lists and a calendar) in one of these content place holders (the 'menu content place holder'). In my content page I've set the 'menu content place holder' to 'Default to Master page content'. In my 'main body content place holder' I've included several controls (table, labels) which depend on the user selected items in the 'menu content place holder'.
After including a reference in all the necessary places- like this:
DropDownList ddlList1 = Master.FindControl("ddlList1")
as
DropDownList;
I still get the following exception (this exception occurs in my content page):
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:
[Code]....
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Dec 15, 2010
let me see if I can explain this clearly. I have a gridview control
and I am trying to use the Edit function. In my gridview, there are numerous rows. I pick one to change and click Edit. I then see the boss name in my gridview and click "Change". When I click Change, I'm expecting two fields to appear, one is a label, the other is a DropDownList. I get this error when I click:
System.NullReferenceException was unhandled by user code
Message=Object reference not set to an instance of an object.
Source=App_Web_lzmklgbg
StackTrace:
at Training_TRManageOrg.LinkButton1_Click(Object sender, EventArgs e) in d:projectsediting.aspx.cs:line 108
at System.Web.UI.WebControls.LinkButton.OnClick(EventArgs e)
at System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument)
at System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
InnerException:
Gridview HTML:
<asp:TemplateField HeaderText="Director">
<EditItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("director") %>'></asp:Label>
<asp:LinkButton ID="LinkButton1" runat="server" OnClick="LinkButton1_Click">Change</asp:LinkButton>
<asp:Label ID="Label4" runat="server" Text="Director" Visible="False"></asp:Label>
-
<asp:DropDownList ID="DropDownList2" runat="server" DataSourceID="trDirector"
DataTextField="name" DataValueField="id" onselectedindexchanged="DropDownList2_SelectedIndexChanged"
Visible="False"></asp:DropDownList>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("director") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
Code Behind:
protected void LinkButton1_Click(object sender, EventArgs e)
{
DropDownList DropDownList1 = ((DropDownList)FindControl("DropDownList1"));
DropDownList1.Visible = true; // this line is where the exception occurs
Label3.Visible = true;
}
I figure I must be overlooking something so I'm asking what am I missing?
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Nov 18, 2010
I have a user control with GridView. GridView template has label that suppose to get custom object value Name.
aspx:
<asp:Label ID="lblImage" runat="server" Text='<%# MyData.Name%>' />
cs:
public MyObject MyData;
During page loading MyData object is null, so I'm getting exception: "Object reference not set to an instance of an object.".
How to avoid the error?
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Oct 19, 2010
I am stuck into a problem, i have a user control ProductListing.ascx that contains ListView binded to an object datasource, SelectMethod and SelectCountmethod are provided as well. Everything works fine but the problem started when i add another user control declarativlly Filter.ascx in the productListing.ascx. I want to assign value to a public property MaxPrice in Filter.ascx. I am trying to set this property in the SelectMethod of ObjectDataSource. Usercontrol "Filter.ascx" throws null reference exception when i try to set its MaxPrice Property.
I tried to acced the usercontrol in Databind method of ListView , it is accessible here but viewstate is empty at this point, i saved the value in viewstate in SelectMethod of objectDatasource but i cant access viewstate in ListView Databind. Its empty. Its a simple code and no rewriting to viewstate elsewhere.
Important: My Codebehind files are in a seperate project and .ascx files in seperate project
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Aug 20, 2010
I developed a page in VWD 2008 and it works perfectly locally, but when I deployed it on the server every Page.FindControl() call is causing the NullReference Exception "Object reference not set to an instance of an object. " Can anyone help me out? Code is below
[Code]....
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Nov 2, 2010
So I have followed this tutorial to try and me edit a record in a datalist.
[URL]
When I click update after updating anyfield it throws a NullReferenceException was unhandled by the user code. Here is my code.
protected void DataList1_UpdateCommand(object source,
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