C# - ViewState ["sample"] Variable Not Retaining Value On Postback In A Composite Control?
Oct 18, 2010
I have created a composite control with sample details as follows. Basically, the first time on page load the control sets a view state variable and the problem is that on post back (when the button is clicked), the ViewState variable is null. I have researched extensively and I am not able to find a solution. I checked all the Microsoft recommended articles and also from other developers. This approach seem to work for everyone
PS: This code may not work as it is only for illustrative purposes. but this is exactly what i'm doing in my code.
Public class Test : CompositeControl
{
private Button btnTest = new Button();
public string TestViewState[code]....
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Oct 29, 2010
I have a composite control that has a couple of private fields that reference values in the cache and these private fields are called during the constructor method. Since a string key is used to identify the value in the cache, I must have a way of storing that string key in such a way that it is available at the time the control is instantiated, and I have to be able to reference it on postbacks without it changing.
In addition, this key is generated the first time the control is loaded, but it should not be changed again after that first time.
How can I accomplish this?
I have already tried saving it to viewstate, but that doesn't work because viewstate is not yet available at the time the control is instantiated.
I have tried using a private field and then checking against Page.IsPostback in the constructor and if it isn't postback, I assign a value to the private field, but on subsequent postbacks it looses it's value, and I can't reassign it in the Page.IsPostBack again because it is an autogenerated GUID.
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Jan 19, 2010
i have a <input id="FILE_UPLOAD".....................> file upload html control in my asp.net web applicationwhen a post back occurs the data entered in the control gets lost . how do i retain the data entered
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Aug 21, 2010
I want to write own control which can contain other. And I want to define content of the control in the .aspx file where the control is defined. I have written such control. But now I have issue with ViewState of inner controls of my control. The following samle illustrates the issue: I defined two asp:DropDownList ID="ddl1" and ID="ddl2" One of them is inside of my control and other is outside. When posback is occurred asp:DropDownList ID="ddl1 loses state and becomes empty. How to say ASP.net to store state of inner controls defined by this way?
MyControl.ascx:
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="MyControl.ascx.cs" Inherits="DynamicControls.Controls.MyControl" %>
<div class="box"> [code]....
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Nov 17, 2010
I am trying to make a simple composite control - just a label and textbox - but the postback isn't being picked up by the control.I haven't implemented IPostBackDataHandler as according to this its not necessary - the TextBox control should tie in automagically. A composite control that includes a TextBox need not worry about postbacks, as the embedded control will work it out with ASP.NET automatically.
class TestControl : WebControl
{
Label _label;
[code]...
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Feb 23, 2010
I am building a composite server control that currently only has a TextBox and a DropDownList. Here is the code in all its foetal glory:
[Code]....
The control appears to work correctly across postbacks, that is until declarative values are set, e.g.:
<squee:Address runat="server" ID="a" Street="123 Fake St" State="VIC" />
After this, the text box continues to work correctly, but the _state member does not pick up the posted back values and instead just sticks to the declared value. I've checked the raw posted values in the Request object, and the new value for the list's UniqueID is there, but _state doesn't pick it up.
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Feb 3, 2010
My problem is that I have an ASPX page which contains an ASP:Table. The rows for the table is added dynamically on Page_Load. One column in the table contains TextBoxes, BUT when I type something on a TextBox and cause a postback, I am unable to find the value just entered. And above that the table is not displayed after the postback.Can anyone help me please? I want to keep the table viewstate with the modified textbox values, so that when i post back to server, I can intercept these new values.
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Feb 9, 2010
I want to be able to find the old value of a asp.net control (textbox, checkbox etc) without relying on events (e.g. OnTextChange event). Something like "someTextboxControl.OldText" would be perfect! I imagine that it is stored in the viewstate and need to somehow get at it via a custom control.
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Feb 12, 2010
I have a problem with ViewState. I have an aspx page that has a treeview on the left and an UpdatePanel with an ASP.NET Panel inside on the right. It is in that inner Panel where I load and unload dynamically user controls. I use that update panel to load dynamically controls.
I also made a custom control for my user controls because I need to pass some values from page. On that constructor I use ViewState to store these values.
The first time I load the user control I call its constructor with parameters. When I reload that user control on each postback I use its normal constructor.
My problem is I the values I've stored on ViewState has become null on successive postback.
Update:
This is a piece of my user control:
public class MyUserControl : System.Web.UI.UserControl
{
private int PKId
{
get { return ViewState["pkId"] as int; }
set { ViewState["pkId"] = value; }
}
public MyUserControl(int pkId)
{
this.PKId = pkId;
}
...
}
I'm following this article to load controls dynamically: http://msdn.microsoft.com/en-us/magazine/cc748662.aspx#id0070065.
Second Update:
I also set the same control ID when I load the user control at first time and on each reaload.
Maybe I can use another method to store these values like input hidden fields or Cache. I've choosen ViewState because I don't want to overload server with Session values for each user.
Third update:
I load the controls with this code:
System.Web.UI.UserControl baseControl = LoadControl(ucUrl) as System.Web.UI.UserControl;
if (baseControl != null)
{
baseControl.ID = "DestinationUserControl";
PanelDestination.Controls.Add(baseControl);
}
And reaload with this code:
DynamicControls.CreateDestination ud = this.LoadControl(TrackedUserControl) as DynamicControls.CreateDestination;
if (ud != null)
{
ud.ID = "DestinationUserControl";
PanelDestination.Controls.Add(ud);
}
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Mar 25, 2011
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Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
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Oct 23, 2010
When we disabled the viewstate in gridview its lose value but this case not true with Textbox control why?
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Feb 2, 2010
I have a name textbox, label, usercontrol, submit button in my page inside a master page. when the button is clicked iam using the label to show the user "Please enter name". But any postback happens inside the user control then this lable gets cleared, how to retain the value on the postback of the user control.
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Aug 27, 2010
I have a page with 2 dropdown menus and 2 datagrids.
The datagrids get populated by a database based on a dropdown menu slection.
This page links to another page which in turn links back to the original.
If the user leaves the first page and then returns back I want to keep the dropdown menus and datagrids populated.
I tried doing this with session variables but can't get the datagrids to stay populated ...
[Code]....
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Nov 25, 2010
I created checkbox in a gridview. I hope to retain the checkbox value after postback.
[Code]....
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Aug 1, 2010
Platform: ASP.Net 2.0 I have multiple checkboxlist controls on a webpage. Along with that i have the same number of buttons on that page. Initially all the checkboxlist controls are hidden. When user clicks on a button, corresponding checkboxlist controls gets visible making others hidden and allows user to select the options.
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Nov 15, 2010
I have a ASP DropDownList that gets populated on the Page_Load event, after i select an item and hit a button the selected item gets cleared and the first item in the DropDownList gets selected. (The DropDownList is only populated when the page is not postback)
if (!IsPostBack)
{
List<Country> lCountries = new List<Country>();
List<CompanySchedule> lCompanySchedules = new List<CompanySchedule>();
this.Load_Countries(lCountries);
[code]...
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Feb 24, 2011
I have a project in VB.NET which is working fine which essentially has a Datagrid that has a TemplateColumn included which is a column of Checkboxes. The code to declare the datagrid is here...
<asp:datagrid id="dgDates" OnItemCommand="gridEventHandler" BorderColor="Black" BorderWidth="1px"
CellPadding="3" runat="server" AutoGenerateColumns="False" HorizontalAlign="Left" AllowSorting="True"
OnSortCommand="SortData" OnItemDataBound="gridItemDataBound">
<HeaderStyle Font-Underline="True" Font-Bold="True" HorizontalAlign="Center" ForeColor="Black"
BackColor="#D4D0C8"></HeaderStyle>
<Columns>
<asp:BoundColumn DataField="strParameterName" SortExpression="strParameterName" HeaderText="Parameter Name"></asp:BoundColumn>
<asp:BoundColumn DataField="dtParameterValue" SortExpression="dtParameterValue" HeaderText="Parameter Value"></asp:BoundColumn>
<asp:TemplateColumn HeaderText="Constant" SortExpression="blnStatic" ItemStyle-HorizontalAlign="Center">
<ItemTemplate>
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</ItemTemplate>
</asp:TemplateColumn>
</Columns>
as you can see the Checkbox has Autopostback="true" but there are other things on the page which produce postbacks as well.
My Page_load has this in it, being called on every load of the page, postbacks included...
Dim strGUID As String
strGUID = Session("strGUID")
dgDates.DataSource = SqlHelper.ExecuteDataset(ConfigurationManager.AppSettings(Web. [Global].CfgKeyConnStringADMIN), "dbo.spRptGetSchedulingDates", strGUID)
dgDates.DataBind()
intNumberOfDates = dgDates.Items().Count
as well my code behind has the following code for the gridItemDataBound
Protected Sub gridItemDataBound(ByVal sender As System.Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs)
'hide the intRptSchedulingDatesID for each row in the checkbox's content style variable
If (e.Item.ItemType = ListItemType.Item Or e.Item.ItemType = ListItemType.AlternatingItem) Then
CType(e.Item.FindControl("cbStaticRolling"), CheckBox).Style("Content") = CType(e.Item.DataItem, System.Data.DataRowView).Item("intRptSchedulingDatesID")
End If
End Sub
everything you see sbove is working perfectly fine...in the sense that when I click one of the checkboxes, the page_load fires, the gridItemDataBound fires on DataBind() and when all is done, the checkbox retains the value that the user clicked the checkbox.
With all this exact same code converted to C#....the events all fire in the same order, but the checkbox selected value always clears...any thoughts??
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Jan 13, 2011
I have a couple of RadioButtons that are created dynamically. But after postback they don't retain their checked property. I also have some CheckBoxes and they work just fine using the same mechanism (code below). I have narrowed down the problem to the "GroupName" property. If I remove it, it works just fine. But I need the RadioButtons to be mutually exclusive.
[Code]....
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Dec 16, 2010
I want some sample code that will loop through records of table variable using a forward only cursor.
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Oct 9, 2010
Now here is the weird thing. First i am running it locally on the built in vs2008 web server.I load my control in fine, do a postback from a linkbutton, locally on my machine it all works fine, no issue.However when it goes onto my host, it falls over with the message:
Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request.Now i also load controls dynamically and use postbacks and things in the admin area of the site...and that works fine, however my front end just keeps failing? See the code behing below:
[Code]....
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Dec 14, 2010
Does ADO.Net Entity Framework 3.5 support Composite Foreign key/Composite primary key?
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Jun 9, 2010
I have searched the web for the answer and saw that mostly variables are saved in viewstate on page.prerender event. Then the value of the variable is set back in page load event.However, when I save a variable in viewstate on prerender or load events, how can viewstate store the value of the variable after it is changed dynamically on codebehind?
Let's say, after page is loaded, user clicked a button which changes the value of the variable in its onClick event. Then the postback event raised since the button was clicked. According to me, the new value should have been lost and cannot be saved in the viewstate if the variable is saved in the viewstate only in prerender event. Because on postback the prerender event wont fire and the value cannot be saved.
Shouldn't I save the variable in the viewstate just before the postback event rises?? If so, how can viewstate store the new value of the variable if the viewstate is saved in prerender event?
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Jan 11, 2011
i create new composite control to make a full calendar control.
[Code]....
All is good until i put
[Code]....
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Feb 12, 2010
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