I have an asp ListView that is currently bound to an ObjectDataSource. The ObjectDataSource's select method has a parameter that is tied to a hidden Label. Thus to clear my ListView I simply have my hidden Label's text property set to string.Empty and bind the ListView's data. This works great, however if a user clicks one of my ListView <th> Labels, which sorts the ListView, and then clicks the "Clear" button it throws a System.IndexOutOfRangeException: Cannot find column name.
This is the only time this Exception is thrown, if the ListView is cleared without being sorted first everything is hunky dory.
Any help is appreciated
I presume that when the label is blanked your datasource is returning nothing, not even a table schema. This will mean that your ListView will have no data including no concept of what the columns might be. Thus when you are telling it to sort on a certain column it is complaining that it can't find that column.
I would imagine the two easiest fixes would be to remove the sort column when you clear it or to make sure that the ListView always knows what columns it has at least.
In your Clear() method are you iterating through or using a specific column name to delete the items?
Related
I want to do something really simple, I just can't seem to find the EnableClientAddRow property, so I can set it to true. I have a standard GridView control on a web form. I want a button to appear on the web form. When the user clicks the button, an empty row is added to the GridView UI, so the user can enter data in the appropriate fields. The row will of course, have a "Save" button of some type in one of the columns.
I know this functionality must be in the GridView somewhere, I just can't find it. I did find some odd hacks that try to manually implement this. I'm not really interested in footer manipulations or binding tricks, just the standard add row method.
EDIT:
It appears the GridView does not support adding a row as a first-order operation. This appears to be a serious design flaw.
I typically add a new record to the underlying data source as a part of the "add record" button click action. I then re-bind the view in order to show the blank row.
The new record is typically a DataRow if the GridView is bound to a DataTable, or an object if the GridView is bound to a collection of a particular type. Not sure if that is what you consider a binding trick from your question, but it works well and is quite easy to implement.
Edit - more detail to describe the process:
Add the row to the data source, set the EditItemIndex to the newly added row in order for the row to enter edit mode, then bind the data source to the GridView. Your EditItemTemplate would contain a Cancel and a Save button. Cancel would re-bind the GridView to the underlying data source without the empty row and set EditItemIndex to -1, thereby removing the row from the GridView.
How to easily insert row in GridView with SqlDataSource
If you add a new row to the datasource, even if the row has empty values, and you databind the datasource to the Gridview, it should show up as an editable row just like any of the other rows.
I have a gridview full of telephone numbers. To populate the gridview I bind the gridview's datasource to a List<> of telephone numbers. I do this when the page is first loaded, but not on postbacks.
I want the user to be able to delete some of the telephone numbers, and then, if they want, click a Save button, and this will update the database, otherwise their changes will be ignored. So I have a button in the grid, and an event is fired, and I can call DeleteRow(row index) and remove the row from inside this event. For some reason this doesn't work.
All the gridview examples I find on the Internet execute the delete straight away by calling an sql function, and then bind again. And some examples bind the grid every time the page ios loaded, which seems inefficient.
My questions is:
The delete button causes a postback to the server. On postback the list of telephone numbers no longer exists. And the gridview's datasource is null. The grid is no longer bound. But there must be data somewhere, because the data in the grid is still visiable. Where is this data, and can I delete a row of it, so that a row in the gridview is deleted?
The viewstate saves the contents of the datagrid, so the answer is "The Viewstate"
Understanding the viewstate is essential to understanding how ASP.NET works, so rather than posting just enough info to answer your question, I'm going to recommend you read the entire article I linked to.
You can use jquery , you need to save the Datakey value of each deleted row in a hidden field
and hide the selected row , and when user clicks save , u can delete the rows based on hidden field values # code behind.
I've an ASP.NET dropdown list and getting selected value by using the .SelectedValue. I also set this value in some cases by assigning to it. I seem to be randomly not getting this value set even when I choose the item from the drop down. Sometimes it works and sometimes it doesn't.
Ideas?
I you are binding your data at Page_Load make sure you're not re-binding by checking if page is post back.
if(!Page.IsPostBack){ /*bind data here*/ }
Make sure you are not re-binding the data on postback before you are able to check the selection.
Also, are you creating listitems and inserting the listitem into multiple lists? If you select one list, it will change the other.
I am updating an existing ASP .NET site. This site has a custom grid control class that extends the GridView control to add a few features. Many pages in the site use the built in declarative two-way binding feature that is built into the base GridView, i.e. column templates make calls to Bind() so that data can be shown and updated automatically. This works fine in most cases. However, when binding DropDownList controls there is now a problem.
Recently I had to add a feature that allows records in some tables to be marked as 'Closed', i.e. they can no longer be referenced by new records being inserted into other tables.
When editing a data grid row that has a DropDownList of child records that can be closed, the SelectedValue property might be bound to an ID that does not exist in the list. This causes an ArgumentOutOfRange exception to be thrown. I just want the DropDownList to default to no selection if the record is closed and therefore not in the list.
I'm looking for the easiest way to solve this. If possible I don't want to have to make a lot of changes to existing code.
I can programmatically set the selected index of the DropDownList in the RowDataBound event. But I can't find a way of updating the value whilst keeping the existing update functionality.
The actual question:
Is there some way to extend the DropDownList to make it ignore invalid values for the SelectedValue property? The only example I have seen so far does not work. I think that the DropDownList caches the value in case it has not yet had its DataSource property set, so overriding the SelectedValue property is not sufficient.
Alternatively, if there is a way to use the OnRowUpdating event to manually add the data to the update then that would be OK. I have tried adding values to the NewValues dictionary on the GridViewUpdateEventArgs class but it doesn't seem to work. Note that the grids are bound to lists of objects, not DataSourceControl derived controls.
Any help would be appreciated. Thanks.
If anyone's interested, I think I solved this by overriding the PerformDataBinding method and catching the ArgumentOutOfRangeException there. I suspect that the SelectedValue property might need to be overridden as well if the order in which the two properties are bound can vary.
Well i have a gridview where i have defined the columns on my own and turned autogenerating off but now i have the problem that i cant access GridView.SelectedRow.DataItem.
As it turns out to be null now, when it had a value when auto generation was turned on..
Edit:
What i need is a way to save the ID of the row while not showing the ID to the user so if there is any way to do this?
I'm guessing DataItem is only properly filled when you are using DataBinding.
Are you using DataBinding?
Ok from this url:
The GridView (and actually, all our
data controls) does not save data
items across postbacks. This reduces
ViewState (if the objects are even
serializable) and enables garbage
collection to happen and clean up your
objects. So, when you click the
button to post back, the GridView has
not called DataBind and therefore your
data item isn't there. This is what
you've discovered.
Guessing you're reading the value from a postback, might just be the problem.
Try using SelectedValue, if you've setup the (primary) key for the items.
I've always used that and it worked.
msdn about SelectedValue
You can create a new hidden template column that will have a label with the ID . and in the cs file you use .FindControl on the rows.
You also have DataKeys property on the gridview, witch I think also does what you want