Having an issue with an ASP.NET GridView is empty on postback that I need some help with. I think it may have something to do with the ViewState not being setup. Anyhow I originally had the code working on single user-form until I refactored code.
Now to paint the picture I have now both a master page and a base form. My master page has the place holder and on my actual user-form I have placed the GridView within the place holder bounds as follows:
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolderMainBody" Runat="Server">
<asp:GridView ID="data" runat="server" AutoGenerateColumns="false" EnableViewState="true" ...>
...
</asp:GridView>
</asp:Content>
One of fields in the GridView is an editable comments field mutli-line textbox (the rest are non editable):
<asp:TemplateField HeaderText="Comments">
<ItemTemplate>
<asp:TextBox ID="TextBoxComments" runat="server" TextMode="MultiLine" Rows="4" Columns="40" Text='<%# Bind("Comment")%>' />
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="TextBoxCommentsEdit" runat="server" TextMode="MultiLine" Rows="4" Columns="40" Text='<%# Bind("Comment")%>' />
</EditItemTemplate>
</asp:TemplateField>
I edit one of the rows and click a submit button to postback. The GridView has 10 rows to enter into however on postback there are zero rows so my saving is lost!
My base form contains the code in the OnInit event to load the submit button and thus also handles the click event.
My OnLoad event I call the base Onload which inturn calls my user form's Page_Load handler code which has one line of code namely:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
MyBase.data = Me.data
End Sub
and in the BaseForm is declared as:
Protected WithEvents data As GridView
Protected Overrides Sub OnLoad(e As EventArgs)
MyBase.OnLoad(e)
If Not Page.IsPostBack Then
...
BindData(...)
...
End If
End Sub
in this way I can also handle all GridView events in the BaseForm.
So somewhere between the master/baseform/userform/viewstate relationship my GridView data is lost on PostBack. Any ideas?
On your Page_Load, bind the data only if IsPostBack is false.
You click on submit button that submit button fire RowUpdating event and that event contain query for update database table and after executed update query call BindData() function in your code .
Three in row I think for myself answering my own question - hooray! I do not know if that makes me intelligent or dumb because I have to search for more that a day to find a solution. Perhaps I did not give out enough information or it was not clear and this is what happens when you do things for the first time and you do not have a clue what you are doing. The vital information which was maybe not implied but hinted at, which I will spell it out for anyone else that might have the same problem, is I left out mentioning in my OnInit method I call the following code:
Dim cpl As ContentPlaceHolder = Master.FindControl("ContentPlaceHolderFooter")
btnUpdate = New Button
btn.ID = "btnUpdate"
cpl.Controls.Add(btnUpdate)
I know the purest will say why did you not add the button to the footer of the grid as opposed to an additional content placeholder in the master page - well with egg on my face I didn't.
Anyhow I moved the code above to the CreateChildControls overridable method and I also required an additional call to EnsureChildControls in my OnLoad event so my OnInit method with emphasis disintegrated!##%^* Why? Well the answer was hinted at within the answer to the other question asked on this site I mentioned in my second comment to "Rajan Chauhan" that I checked out and that is apparently whenever you iterate through the collection of controls you mess with the ViewState (hey I am just re-iterating what was said in the other post I have no authority on the matter) before it gets loaded so calling Master.FindControl is a no-no inside OnInit!
However, saying all that my RowUpdated event does not fire as I am actually editing in view mode because of my ItemTemplate markup so I will stick with what I have as my btnUpdate_Click event still works as before i.e. it does some magical code that I found on some other site that checks each row one by one for change of data and then updates that particular row only. Well I can as there is only 10 rows at most so I do not overload the ViewState too much and if it is important to know I also use paging so in reality I have more than 10 rows but did not want to mention that as I thought that might add to the confusion.
Related
I have a JS function in an ASPX page that performs a __doPostBack to a vb.net code behind. The problem is that it is forcing the page to refresh. How can I prevent this? My code below...
JS:
__doPostBack('', 'test');
VB.NET:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If IsPostBack Then
Select Case Request.Form("__EVENTARGUMENT")
Case "test"
RadMediaPlayer1.Source = url
End Select
End Sub
Thanks!
There is one easy way, and then one hard way.
The first issue? asp.net web pages are in fact designed to near ALWAYS have and endure post-backs.
This quite much means that any button, any combo box, or just about anything on that page to run some code behind WILL cause a page post-back.
And thankfully due to automatic "view state" management, most controls, and even a grid view, or even a combo box selection will correctly maintain its values for you (its view state).
So, if you don't want the whole page to post back and refresh?
Then you can drop in a plane jane asp.net button, and say whatever it is you want to "only update", then try using what is called a update panel.
Try a quick test page like this:
<form id="form1" runat="server">
<div>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<br />
<asp:Button ID="Button1" runat="server" Text="Button" />
</div>
</form>
And our code behind like this:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
End Sub
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
TextBox1.Text = Date.Now
System.Threading.Thread.Sleep(700)
End Sub
Now, I put in a 3/4 of second delay - just to help you see the effects of this (you don't want that delay sleep() in your actual code.
Ok, now run the above page, click on the button. You see the traditional post-back, you see the browser "spinner"/wait occur, and then the text box is updated.
Now, lets use what is called a update panel - and I am going to suggest you try one.
You can even dump/drop the JavaScript you have now.
So, you have to drop into the page a script manager, and then move your content inside of he update panel. It will now look like this:
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<div>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<br />
<asp:Button ID="Button1" runat="server" Text="Button" />
</ContentTemplate>
</asp:UpdatePanel>
</div>
</form>
Give above a try - note how the page don't post-back any more? How cool is that!!!
So, add update panel, content template. And move your button, and the adMediaPlayer1 into that panel.
You don't even need to adopt any JavaScript here. Drop in a plane jane button, and just have normal code behind for that button. Say like this:
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
RadMediaPlayer1.Source = "some real url goes here"
End Sub
A few things:
While this looks, feels and appears to NOT do a post back and the .net system will wire this up for you automatic - VERY much like a ajax call?
Don't put too much inside of those update panels.
and keep in mind, while this does not seem to do a post back? In fact this results in what we call a "partial" post back. The page load event even will fire.
Note that code behind CAN ONLY now modify controls inside of that update panel. Other controls on the page are off limits. (unless you move them into that update panel also).
But, dump your JavaScript button or code for the post back. Just move in the media control and your button to inside of that up date panel. Give this a try - you not see a post back - you not see the browser "spinner"/wait run at all.
This feature is great - but a not a cure all.
The next way to do this?
Is you can setup what is called a ajax call. This can call code behind, but keep in mind the code behind can't update controls on the page (due to no post-back). If you don't do a post-back, then code behind can't touch controls on the page.
This would suggest that you have a client side button - click on it, it runs JavaScript, calls some code behind, code behind returns a result, and then in JavaScript you stuff/change the URL of the given control. Since you changing that URL in pure JavaScript at this point? You probably don't even need to write or call code behind anyway.
but, try the update panel - they are very useful. But, keep in mind behind, the .net system is doing a bit of fakery to achieve this goal, and what a partial page post- back does occur.
Edit: pass value from js and click button
So, as noted, if you have a post back, you get page refresh!!! - that's what the command does and means!! So, you can't say I dont want to post back and not refresh the page, and then do a post back!!!
However, as noted, your js code is "obviously" a much larger example, and you sharing of JUST the __DoPostBack() in js is as you noted a larger set of code and routines here.
However, I still suggest you use a update panel.
You can keep 99% of your js code now, and just remove the _dopost back.
Move your case statement code to a button. (yes, a button click code stub).
What we THEN do is this:
The js code can figure out and do whatever it needs. Obviously we reach a point in which a VALUE of some type has to be passed to the server. And then what we will do is then use js code to CLICK the button - the ONE inside of the update panel. This will and should prevent a page refresh. And we pass the value by using a asp.net hidden field control (you could even use a hidden text box - but it don't matter - hidden field is probably better).
So, the pattern, and code will look like this:
We drop a button, hidden field, and that other video or whatever control is is the page - all inside the update panel.
then your js code? It runs, gets the final value. We shove that value into a hidden field control, and then use js to click the button - also inside of that panel.
Thus, you move your on load code + case statement to the button click code.
Like this:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
End Sub
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
' get value passed from js
Dim strMyValue As String = Me.HiddenField1.Value
Debug.Print(strMyValue)
Select Case strMyValue
Case "test"
Case "zoo"
Case "my fun test"
End Select
End Sub
And the markup is this:
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<div>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<br />
<asp:Button ID="Button1" runat="server" Text="Button" ClientIDMode="Static" />
<br />
<asp:HiddenField ID="HiddenField1" runat="server" ClientIDMode="Static" />
</ContentTemplate>
</asp:UpdatePanel>
<asp:Button ID="Button2" runat="server" Text="js post back"
OnClientClick="mypost();return false;"
/>
<script>
function mypost() {
// set value to pass to button click
$('#HiddenField1').val("my fun test")
$('#Button1').click()
}
</script>
</div>
So, in place of your doPostback, you set the hidden field, and then with js click the button. (once you get this workng, then hide the button with style="display:none"
Of course, you proably have a bunch of postback in your code.
So, make a js function called MyPostBack, say like this:
function MyPostBack(sValue) {
// set value to pass to button click
$('#HiddenField1').val(sValue)
$('#Button1').click()
}
Now, you can replace all your _DoPostBack('', 'test')
With MyPostBack('test')
So, in the update panel, put the hidden field, the button, and that other control. And your js code will now "click" that button in the panel.
Note that the js code above does assume you using jQuery. However, you can code in pure js, and not necessary use jQuery short hand as I did above.
I've found this question asked countless times, but the answers haven't worked for me:
I have an asp:Dropdownlist that is dynamically bound from an asp:Objectdatasource. A button calls a codebehind function to store the selected value. However, in the click event function the value of the dropdown is always reset to default, AFAIK due to a postback that is called before the click event handler. When debugging I've checked that ViewStateMode is enabled and EnableViewState is true. I've been stuck with this for hours now, does anyone have a clue?
ASPX markup:
<asp:DropDownList runat="server" DataSourceID="AvailableNivamalerODS" ID="AddNivamalerDDL" />
<asp:ObjectDataSource runat="server" ID="AvailableNivamalerODS" TypeName="Nivamaler.NivamalerPresenter"
SelectMethod="GetAvailableNivamalers"></asp:ObjectDataSource>
<asp:Button runat="server"
Text="Legg til"
OnClick="AddNivamalerToTjstpl"
ID="AddNivamalerBtn"
UseSubmitBehavior="False"
CssClass="ui-button ui-widget ui-state-default ui-corner-all ui-button-text-only"/>
Codebehind
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
If Not Page.IsPostBack Then
AddNivamalerDDL.DataBind()
End If
End Sub
Click event handler:
Protected Sub AddNivamalerToTjstpl(sender As Object, e As EventArgs) Handles AddNivamalerBtn.Click
Dim nivamalerId As Integer = AddNivamalerDDL.SelectedValue
'Here nivamalerId is always the default value
End Sub
Cheers!
EDIT
The replies to previous question have basically said to put the data binding in the Page_Init method or the Page_Load method after !IsPostBack, which didn't help me.
Also a disclaimer: This is a legacy project with tons more code (the relevant code is new), but I tried to snip out the relevant bits. As far as I can see the rest of the code shouldn't affect this, but I can't be certain as I am still fairly new to ASP.Net
Put your page_load code into the page_Init section. The asp lifecycle will make the dropdown list databind() be absolutely meaningless if it is in the page load section here because a Postback causes the whole page to resubmit itself to the point of page_load and since you have the if not ispostback statement, it will reload the page structure but won't run your page load code and that is where you are losing your value. Other than that the code is fine.
I solved it, and as has been pointed out, the posted code is incomplete: The dropdown is inside a JQuery-ui dialog, which makes the dropdown lose its state. I ended up with a workaround with a Javascript function which copied the selected value to a hidden field outside the dialog and using the hidden field value in the codebehind
I'm looking for a solution for the textbox leave event in asp.net vb.net.
I have searched but Didn't get the right solution, what I'm actually doing is.
I have textbox in which a user write the Product Id number however the focus moved from the textbox then all the related data should be displayed on the concern textboxes.
Their is no textbox_lostfocus event or textbox_keydown event available in ASP.Net. You can do the same by writing the code in TextChanged event of the Text Box.
Your code will be like the following :
Private Sub txtamount_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtamount.TextChanged
//Your code comes here
MsgBox(txtamount.Text)// sample display
End Sub
This code will give result only when you add AutoPostBack ="true" with your Textbox design.
ie., the ASP code for the textbox will be :
<asp:TextBox ID="txtamount" runat="server" AutoPostBack ="true" />
Hope that this is actually your are asking for.
I have a quoting system that can generate several variants of a quote. these quotes are displayed on a screen for sales staff to compare and choose which is the most suitable. Is it possible to programmatically create a button and click event for each quote that is generated?
Each quote needs a save button and a remove button. both would fire functions and pass in the quite ID.
Can anyone point me in the correct direction for this? the amount of quotes and buttons that could be on the page is limitless.
Many thanks for your help.
Set CommandName and CommandArgumentof your button template and catch the event inside ItemCommand event of your repeater
<asp:Repeater runat="server" ID="rptrQuites">
<ItemTemplate>
<asp:LinkButton ID="btnSave" Text="Save" CommandName="Save" CommandArgument="<%#Eval("QuiteID")"%>></asp:LinkButton>
</ItemTemplate>
</asp:repeater>
and in code behind
Protected Sub rptrQuites_ItemCommand(source As Object, e As RepeaterCommandEventArgs) Handles rptrQuites.ItemCommand
If e.CommandName = "Save"
' Put your code here
End If
End Sub
I am using a standart .net 2.0 Gridview which uses an XMLDatasource to populate the Grid. The Data property of the XMLDatasource is set dynamically which allows the gridview to change based on input.
All this works fine however I am having problems with paging...
I have set the AllowPaging Property to "true" and set the PageSize Property to "10". The GridView populates fine the first time around showing the first 10 records and the number of pages as hyperlinks at the bottom, BUT when i try to click on any of the page numbers to view them a message box pops up saying "Object reference not set to an instance of an object"
any ideas what I'm doing wrong?? or is there anything i need to do which i have missed out on??
Code currently being used;
Gridview...
<asp:GridView ID="GridView1"
Runat="server"
DataSourceID="XmlDataSource1"
AutoGenerateColumns="False"
AllowPaging="True"
style="width:100%; height:100%;"
EnableViewState="False">
<SelectedRowStyle BackColor="Red" />
<Columns>
<asp:BoundField DataField="TYPE" HeaderText="TYPE" SortExpression="TYPE" />
<asp:BoundField DataField="DESCRIPTION" HeaderText="DESCRIPTION" SortExpression="DESCRIPTION" />
</Columns>
</asp:GridView>
XMLDatasource...
<asp:XmlDataSource ID="XmlDataSource1" runat="server" TransformFile="~/XML/grid2.xslt" EnableCaching="False">
</asp:XmlDataSource>
vb.net code which sets the Data property of the XMLDatasource...
Private Sub btnTest_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnTest.Click
XmlDataSource1.Data = _testLib.GetGridXML(_Num)
GridView1.DataBind()
End Sub
where _testLib.GetGridXML is a function that returns an XML string based on the _Num passed in.
It's difficult to say without seeing your code... I would speculate that you assign the Data conditionally, i.e:
If Not IsPostBack Then
MyXMLDataSource.Data = "...some xml..."
End If
In this case it will be empty on post back and you get your exception. Could be something else, but then again, no code...
Update
Since you've added more information...
You must have something like code above on Page_Load. Since you are not providing it here, I presume you do. If you don't, you'd get the null reference exception on each load.
With that in mind, you assign data on some button click, but not on PageIndexChanging.
You click the button, the page loads, you assign the data, the grid shows it. Then you click the grid's next link, the page loads again, PageIndexChanging gets fired, your click event doesn't -- where's assignment then?
From what I see, either assign the Data property on Page_Load every time or do it in all subsequent events, i.e. on page change, on sort, etc.
Btw, you don't have to call DataBind when assigning XmlDataSource declaratively.
It should work if you do your databinding on the PreRender event
Since the XML datasource is being set dynamically if you set it on the PageLoad all the page elements might not exist at this stage.
Are you implelenting the OnPageChanging Event ? Normally you need to implement it and use the e.NewPageIndex property from the Event Argument to set it in your gridview.