A few days ago, I wrote about issues with implementing a ListView in ASP.NET. Now, with all of the other code written, I'm having trouble saving changed items in a ListView.
A few things of note:
The Save button is not part of the ListView proper; it calls the GetListViewItems() method, which in turns call the Save() method.
The Listview.DataBind() event is invoked when a button is pressed requesting the records to be updated
The Listview shows text using <%#Eval("Key.Name") %> and a named DropDownList using <%#Eval("Value") %>
Getting The Items From the ListView
public void GetListViewItems()
{
List<Foo> Result = FooManager.CreateFooList();
DropDownList ddl = null;
ListViewItem Item = null;
try
{
foreach (ListViewDataItem item in lvFooList.Items)
{
Item = item;
ddl = ((DropDownList) (Item.FindControl("ddlListOfBars")));
if (//something is there)
{
Foo foo = FooManager.CreateFoo();
foo.Id = item.DataItemIndex; //shows null
int barId = int.Parse(ddl.SelectedItem.Value); //works just fine
foo.barId = barId;
Result.Add(foo);
}
}
}
catch (Exception ex)
{
//Irrelevant for our purposes
}
}
DataBinding the ListView
The code to databind the ListView is shown here in my previous question.
Question(s):
Why is it that when I iterate through the ListViewDataItem in the Listview that each item is null?
How can I retrieve the Foo.Id from the Dictionary?
What else might I be missing?
What would I use if I wanted to get that Id Programmatically based on what items were shown? As it is now, the current ListView is shown based on what Foos were selected. Those Foos selected are then displayed, and the user can change the Bar in the DropDownList, hit Save, and those changes are propogated.
Update
As it turns out, my problem was what leppie had said; and that was that I needed to specify DataKeyNames and use those to retain the information from the ListView.
Here's the code I added:
try
{
int DataKeyArrayIndex = 0;
foreach (ListViewDataItem item in lvFooList.Items)
{
Item = item;
ddl = ((DropDownList) (Item.FindControl("ddlListOfBars")));
if (//something is there)
{
Foo foo = FooManager.CreateFoo();
Foo tempFoo = FooManager.CreateFoo();
if (lvFooList != null)
{
tempFoo = ((Foo)(lvFooList.DataKeys[DataKeyArrayIndex].Value));
}
foo.Id = tempFoo.Id;
int barId = int.Parse(ddl.SelectedItem.Value); //works just fine
foo.barId = barId;
Result.Add(foo);
DataKeyArrayIndex++;
}
}
}
And then in the .ascx file, I added DataKeyNames="Key", like so:
<asp:ListView ID="lvFooList" runat="server" DataKeyNames="Key">
This allowed me to use the Key from my previous post to determine which Foo was being looked at.
Any critiques of this approach, as well as methods for making it better are greatly appreciated.
Some quick answers:
Your need to use databinding for that to work, in other words, assign to DataSource and call DataBind(). EDIT: seems you are doing that. But remember it wont persist between postbacks, just the DataKey (see below).
If I recall correctly, you need to specify the DataKeyNames, and they can be retrieved from the DataKey property then.
you can also use the ListViewDataItem.DataItemIndex property instead of keeping your own index, as in:
foreach (ListViewDataItem item in MyListView.Items)
{
// in this example key is a string value
Foo foo = new Foo(MyListView.DataKeys[item.DataItemIndex].Value as string);
// do stuff with foo
}
Related
I have a User Control with an Ultragrid. In a particular form where I add a ValueList. The value list will not show for the particular column I'm interested in. If I then code in another column instead by changing the index value for columns I get the value list in the column.
The code looks like:
private void AddCombo(object sender, UcUltraGen.RowClickArgs e)
{
ValueList vl;
if (!ucUltraGridMain.Grid.DisplayLayout.ValueLists.Exists("Texas"))
{
vl = ucUltraGridMain.Grid.DisplayLayout.ValueLists.Add("Texas");
}
else
{
vl = ucUltraGridMain.Grid.DisplayLayout.ValueLists["Texas"];
}
var row = e.VariantRow;
List<PcBase> list = PcBase.PcBaseList.Where(x => x.VariantId == row.Cells["Id"].Text).ToList();
AddValueList(list, vl);
ucUltraGridMain.Grid.DisplayLayout.Bands[0].Columns[1].ValueList =
ucUltraGridMain.Grid.DisplayLayout.ValueLists["Texas"];
And if I change to
...
ucUltraGridMain.Grid.DisplayLayout.Bands[0].Columns[2]
It works. How can I have changed the behavior of columns[1]?
The property in column[1] was read only that is it only had a "get" implemented. By adding a set it worked. Hope this helps someone.
(Asp.net/C# VS2008)
I have a datagrid populated by a database and when pressing Edit, a form opens and populates fields/controls from that datagrid line.My issue lies when trying to populate a dropdownlist box, which has a datasource from an ENum List.I Just cannot get the text from the datagrid cell to show up in the ddL, it should also equal one of the Enum Items and auto select it.
My Code
Pull from the datagrid cell gives me “Low”
ddl_reg.Text = e.Item.Cells[25].Text;
public void Populate_regstatus_dropdownlist()
{
//if (!IsPostBack)
//{
// ddl_reg.DataSource = Enum.GetNames(typeof(regstatus));
// ddl_reg.DataBind();
//}
//if (!IsPostBack)
//{
// foreach (int value in Enum.GetValues(typeof(regstatus)))
// {
// ddl_reg.Items.Add(new ListItem(Enum.GetName(typeof(regstatus), value), value.ToString()));
// }
//}
ddl_reg.DataSource = Enum.GetNames(typeof(regstatus ));
//ddl_reg.DataValueField = regstatus;
//ddl_reg.DataTextField = "Low";
//ddl_reg .SelectedItem = Enum.GetName(typeof (regstatus ));
ddl_reg.DataBind();
//ddl_reg.SelectedIndex = ddl_reg.Items.IndexOf(ddl_reg.Items.FindByText("Low"));
}
public enum regstatus
{
NotSelected,
Low,
Medium,
High
}
Error received is;
ddl_reg' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value
I am new to C# but through searching your site i realise this means the value is not seen or has not been pulled and would really apreciate some help, or pointing in the right direction, cheers.
I believe the problem is that the drop down list doesn't contain the item you are passing. You may check it before changing the selected value. Other chances are that the value you are getting from e.Item.Cells[25].Text may contain spaces, so you may trim before setting it to the drop down.
if (ddl_reg.Items.FindByText("Low") != null)
{
ddl_reg.Text = e.Item.Cells[25].Text;
}
else
{
//Not found
}
I have quite a few radiobuttonLists in my ASP.net webform. I am dynamically binding them using the method shown below:
public static void PopulateRadioButtonList(DataTable currentDt, RadioButtonList currentRadioButtonList, string strTxtField, string txtValueField,
string txtDisplay)
{
currentRadioButtonList.Items.Clear();
ListItem item = new ListItem();
currentRadioButtonList.Items.Add(item);
if (currentDt.Rows.Count > 0)
{
currentRadioButtonList.DataSource = currentDt;
currentRadioButtonList.DataTextField = strTxtField;
currentRadioButtonList.DataValueField = txtValueField;
currentRadioButtonList.DataBind();
}
else
{
currentRadioButtonList.Items.Clear();
}
}
Now, I want to Display only the first Letter of the DataTextField for the RadioButton Item Text.
For example if the Value is Good I just want to Display G. If it Fair I want to display F.
How do I do this in C#
Thanks
You can't do what you want when you do the binding, so you have 2 options:
Modify the data you get from the table, before you do the binding.
After binding, go through each item and modify its Text field.
So, it you want to display "only the first Letter of the DataTextField for the RadioButton Item Text", you can do:
currentRadioButtonList.DataSource = currentDt;
currentRadioButtonList.DataTextField = strTxtField;
currentRadioButtonList.DataValueField = txtValueField;
currentRadioButtonList.DataBind();
foreach (ListItem item in currentRadioButtonList.Items)
item.Text = item.Text.Substring(0, 1);
If I misunderstood you and you want to display the first letter of the Value field, you can replace the last two lines with:
foreach (ListItem item in currentRadioButtonList.Items)
item.Text = item.Value.Substring(0, 1);
You could add a property to the type that is being bound (the one that contains Good, Fair, etc.) and bind to this property. If you will always be using the first letter, you could make it like so (adding in null checks, of course):
public string MyVar { get; set; }
public string MyVarFirstChar
{
get { return MyVar.Substring(0, 2); }
}
I have a bound dropdown list populated with a table of names through a select, and databinding. it shoots selectedindexchanged that (through a postback) updates a certain gridview.
What happens is, since it runs from changing the index, the one that always comes selected (alexander) can only me chosen if you choose another one, then choose alexander. poor alexander.
What I want is to put a blanc option at the beginning (default) and (if possible) a option as second.
I can't add this option manually, since the binding wipes whatever was in the dropdown list and puts the content of the datasource.
Set the AppendDataBoundItems property to True. Add your blank, then data bind.
ddl.AppendDataBoundItems = true;
ddl.Items.Add("Choose an item");
ddl.DataSource = foo;
ddl.DataBind();
The AppendDataBoundItems property
allows you to add items to the
ListControl object before data
binding occurs. After data binding,
the items collection contains both the
items from the data source and the
previously added items.
protected void SetAddrList()
{
TestDataClassDataContext dc = new TestDataClassDataContext();
dc.ObjectTrackingEnabled = false;
var addList = from addr in dc.Addresses
from eaddr in dc.EmployeeAddresses
where eaddr.EmployeeID == _curEmpID && addr.AddressID == eaddr.AddressID && addr.StateProvince.CountryRegionCode == "US"
select new
{
AddValue = addr.AddressID,
AddText = addr.AddressID,
};
if (addList != null)
{
ddlAddList.DataSource = addList;
ddlAddList.DataValueField = "AddValue";
ddlAddList.DataTextField = "AddText";
ddlAddList.DataBind();
}
ddlAddList.Items.Add(new ListItem("<Add Address>", "-1"));
}
I created this code example using adventure works to do a little practice with Linq and it is very similar to the previous answer. Using linq still shouldn't matter for the answer the last dddlAddList.Items.Add is what you need. "Add Address" = first selected option and -1 = the value.
I'm having trouble figuring out how to add items to a ListBox in WinForms.
I have tried:
list.DisplayMember = "clan";
list.ValueMember = sifOsoba;
How can I add ValueMember to the list with an int value and some text for the DisplayMember?
list.Items.add(?)
Btw. I can't use ListBoxItem for any reasons.
ListBoxItem is a WPF class, NOT a WinForms class.
For WPF, use ListBoxItem.
For WinForms, the item is a Object type, so use one of these:
1. Provide your own ToString() method for the Object type.
2. Use databinding with DisplayMemeber and ValueMember (see Kelsey's answer)
list.Items.add(new ListBoxItem("name", "value"));
The internal (default) data structure of the ListBox is the ListBoxItem.
In WinForms, ValueMember and DisplayMember are used when data-binding the list. If you're not data-binding, then you can add any arbitrary object as a ListItem.
The catch to that is that, in order to display the item, ToString() will be called on it. Thus, it is highly recommended that you only add objects to the ListBox where calling ToString() will result in meaningful output.
You might want to checkout this SO question:
C# - WinForms - What is the proper way to load up a ListBox?
DisplayMember and ValueMember are mostly only useful if you're databinding to objects that have those properties defined. You would then need to add an instance of that object.
e.g.:
public class MyObject
{
public string clan { get; set; }
public int sifOsoba { get; set; }
public MyObject(string aClan, int aSif0soba)
{
this.clan = aClan;
this.sif0soba = aSif0soba;
}
public override string ToString() { return this.clan; }
}
....
list.Items.Add(new MyObject("hello", 5));
If you're binding it manually then you can use the example provided by goggles
The way I do this - using the format Event
MyClass c = new MyClass();
listBox1.Items.Add(c);
private void listBox1_Format(object sender, ListControlConvertEventArgs e)
{
if(e.ListItem is MyClass)
{
e.Value = ((MyClass)e.ListItem).ToString();
}
else
{
e.Value = "Unknown item added";
}
}
e.Value being the Display Text
Then you can attempt to cast the SelectedItem to MyClass to get access to anything you had in there.
Also note, you can use anything (that inherits from object anyway(which is pretty much everything)) in the Items Collection.
If you just want to add a string to it, the simple answer is:
ListBox.Items.Add("some text");
You have to create an item of type ListBoxItem and add that to the Items collection:
list.Items.add( new ListBoxItem("clan", "sifOsoba"));
If you are adding integers, as you say in your question, this will add 50 (from 1 to 50):
for (int x = 1; x <= 50; x++)
{
list.Items.Add(x);
}
You do not need to set DisplayMember and ValueMember unless you are adding objects that have specific properties that you want to display to the user. In your example:
listbox1.Items.Add(new { clan = "Foo", sifOsoba = 1234 });