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Dynamically created Items in DropDownList in GridView not working

I have a .ascx user control on an .aspx page. When the user clicks a button, information is gathered and stored in the database. Then a Gridview is databinded and in the Gridview is a dropdownlist. This dropdownlist's Items are created dynamically based on the users previous input, now in the database. This is all good and the Gridview is displayed with the dropdownlist with the dynamically created Items.
The problem is on the postback for this dropdownlist. I obviously have to recreate the Gridview with the dynamically created Items in the dropdownlist. This does not work. The postback happens and calls the Page_Init and then the Page_InitComplete. This has the databind on the Gridview which calls the SectionGV_OnRowDataBound method. The dropdownlists are recreated. But the SectionDD_OnSelectedIndexChanged method is never hit and then the dropdownlist just reverts back to its original value. I can not change the dropdownlist's selected value.
.ASCX
<asp:GridView ID="MyGV" runat="server" AutoGenerateColumns="False" DataSourceID="MyDS" Width="100%" OnRowDataBound="MyGV_OnRowDataBound">
<Columns>
<asp:TemplateField >
<ItemTemplate>
<asp:DropDownList runat="server" ID="SectionDD" AppendDataBoundItems="True" AutoPostBack="True" OnSelectedIndexChanged="SectionDD_OnSelectedIndexChanged" >
</asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Code Behind of .ASCX
protected void Page_Init(object sender,EventArgs e)
{
this.Page.InitComplete += Page_InitComplete;
}
private void Page_InitComplete(object sender, EventArgs e)
{
MyGV.DataBind();
}
protected void SectionDD_OnSelectedIndexChanged(object sender, EventArgs e)
{
}
protected void MyGV_OnRowDataBound(object sender, GridViewRowEventArgs e)
{
using (EntitiesModel dbContext = new EntitiesModel())
{
// get array[][] array from database
if (e.Row.RowType == DataControlRowType.DataRow)
{
DropDownList sectionDd = (DropDownList)e.Row.FindControl("SectionDD");
sectionDd.Items.Clear();
if (array.Length == 3)
{
if(array[0][2].ToDecimal() > 0) sectionDd.Items.Add(new ListItem(array[0][0], array[0][1]));
if(array[1][2].ToDecimal() > 0) sectionDd.Items.Add(new ListItem(array[1][0], array[1][1]));
if(array[2][2].ToDecimal() > 0) sectionDd.Items.Add(new ListItem(array[2][0], array[2][1]));
}
else if (array.Length == 2)
{
if (array[0][2].ToDecimal() > 0) sectionDd.Items.Add(new ListItem(array[0][0], array[0][1]));
if (array[1][2].ToDecimal() > 0) sectionDd.Items.Add(new ListItem(array[1][0], array[1][1]));
}
else if (array.Length == 1)
{
if (array[0][2].ToDecimal() > 0) sectionDd.Items.Add(new ListItem(array[0][0], array[0][1]));
}
}
sectionDd.DataBind();
}
}
}
}
private void SaveToDB()
{
//save information to database
NOTE
This is one of many ways I have tried to solve this issue. The reason I have saved the information in the database is just a temporary fix. I just want to solve the issue outlined above and then I will add a ViewState solution.

First up, no, you do not have to re-create or load the grid again, or the dropdown list in the post back.
The user can type into the grid - change values, select drop downs. At that point you can loop all the grid rows and get/grab the dropdown values selected.
You CAN of course fire/trigger a event for the dropdown, but it not at all clear if you really need that event here.
If your grid is getting messed up on post-backs?, then it means you not limiting the load up in the FIRST page load - after that, it should not matter.
Say we have this grid markup:
<asp:GridView ID="MyGrid" runat="server" CssClass="table table-hover"
DataKeyNames="ID" AutoGenerateColumns="false" OnRowDataBound="MyGrid_RowDataBound" >
<Columns>
<asp:BoundField DataField="FirstName" HeaderText="FirstName" />
<asp:BoundField DataField="LastName" HeaderText="Last Name" />
<asp:BoundField DataField="HotelName" HeaderText="Hotel Name" />
<asp:TemplateField HeaderText="City">
<ItemTemplate>
<asp:DropDownList ID="DropDownList1" runat="server"
DataTextField="City"
DataValueField="City"
>
</asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="Province" HeaderText="Province" />
</Columns>
</asp:GridView>
And of course non templated fields (such as the first few boundField - they appear in the .Cells collection. but for templated columns, you use findcontrol.
However, in EVERY and NEAR ALL web pages, as a general rule, you ONLY load + mess + create the grid ONE time, and you ONLY do this on the first page load - END OF STORY! You don't follow this rule, then you are in a world of hurt big time.
Ok, so lets load up the grid. Since we have a dropdown, then we have to fill that out on item data bound.
So, our code will look like this:
public DataTable rstCity = new DataTable();
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack == false)
{
LoadGrid();
}
}
public void LoadGrid()
{
using (SqlCommand cmdSQL = new SqlCommand("SELECT City from City Order by City",
new SqlConnection(Properties.Settings.Default.TEST4)))
{
// locd city for drop down list
cmdSQL.Connection.Open();
rstCity.Load(cmdSQL.ExecuteReader());
// now load grid
cmdSQL.CommandText = "SELECT * from tblHotels ORDER BY HotelName";
DataTable rst = new DataTable();
rst.Load(cmdSQL.ExecuteReader());
MyGrid.DataSource = rst;
MyGrid.DataBind();
}
}
Note how I did scope the city table to the class level (no reason to load it over and over for each row - and after the first page load, it will go out of scope - we don't care - it will live during the first page load and the data binding.
Ok, now, lets do the item data bind for the grid.
We have this:
protected void MyGrid_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
DropDownList MyDrop = (DropDownList)e.Row.FindControl("DropDownList1");
MyDrop.DataSource = rstCity;
MyDrop.DataBind();
// get City from current data row source - set the drop to data row City
MyDrop.SelectedValue = ((DataRowView)e.Row.DataItem)["City"].ToString();
}
}
Ok, that's it. (note how the "dataitem" exists ONLY during data binding - a handy tip, since then you have use of the FULL data row - including PK values, and columns that you don't even include in the grid markup. But, once data binding is over, then DataItem can NOT be used - it only EVER exists during the bind process. But this information is VERY valuable, since you have full use of the Actual data SOURCE you used to bind. In above, I needed the City from that Row to set the drop list.
Ok, the output now looks like this:
Ok, at this point since we ONLY bind on first page load. The view state of that grid is 100% automatic handled by asp.net for you at this point in time.
You can drop other buttons on this form - post backs should NOT matter. The BIG lesson here is that gridview does persist (at least it will if we don't re-load it each time on post-back - you should NOT have to re-load).
Ok, next issue:
In most cases, I don't see the need for the dropdown list event in the grid?
So, you can as a general rule select and change any row combo. Once done, then you can get values of each row by looping the data grid rows - including that of dropdown selected.
However, Lets wire up the dropdown list event anyway.
tip of the day:
Since we can't select the dropdown and use the property sheet?
Then in markup do this:
You can in the markup type in OnSelectedIndexChanged=
WHEN you hit the "=" sign, note VERY close how intel-sense pops up a event create option:
So, click on CreateNewEvent - it "seems" like nothing occurs, but in fact if you flip over to code behind, you have a nice event stub created.
So lets put our code in that event - grab the row - show the value just slected.
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
// user changed the combo box
DropDownList MyDrop = (DropDownList)sender;
GridViewRow gRow = (GridViewRow)MyDrop.Parent.Parent;
Response.Write("<h2>Row index is = " + gRow.RowIndex.ToString() + "</h2>");
Response.Write("<h2>Hotel Name is = " + gRow.Cells[2].Text + "</h2>");
Response.Write("<h2>City from Drop selected = " + MyDrop.SelectedValue + "</h2>");
}
Of course we set auto post back = true in the drop markup also - right?
And note how we pick up the "sender", and then use .Parent.Parent to get the grid row that we are operating on. The first parent is some cell or some such.
I actually built recursive function to get that value, but for here we just used .parent.Parent (often with a extra markup, then you need to go op one more .parent).
Anyway, now say I select the last drop down in above, and change it.
I get this output:
In summary:
Only EVER load the grid - first page load - (you check IsPostBack).
You can have all kinds of additional post backs - the grid should survive and just be fine - no need to re-load at all. (GridView has built in viewstate).
Now, after I have fun, change the drop down on many rows?
I can loop the gridview - and any changes to that grid will persist.
In fact, if you make the columns text boxes (in templated fields), then you can tab around and edit almost like Excel, and again the values will persist for you, and they survive post backs. (and then you can send the whole grid of changes back to the database in one update command - I can show how to do this, but this post already has lots of good stuff anyway.
Now, having said the above, having done the above?
Well now that we have this working, then one can go back to building a custom user control - but if done right, it also should behave correctly, and should also survive post-backs.

Populating around 10 Gridviews using one data source ASP C#

I need to display data from one table to 10 gridviews based on a filter value (column).
Lets say colours. So pink grid view should only show items that have Pink in colour column.
At the moment I have one Gridview bound (in ASP) to one Datasource. I am updating the datasource in codebehind.
Something like this:
String selectcommand = Select * from table where subject = "Pink"
sqlDatasource1.SelectCommand= (selectcommand);
mygv.Bind();
Obviously it would be a very bad idea to repeat the same code 10 times, one for each subject. Is there a better way of doing what I am after.
Main question is can I use the same datasorce with many gridviews after changing the colour?
Solution One
I bind all gridviews to one datasource and not bother about filtering by colour.
Then in gridview rowdatabound event of each gridview add something like this
if e.Row.RowType = DataControlRowType.DataRow Then
if e.Row.DataItem("colour") = "pink" then e.Row.visible = False
Any other suggestions?

You're right that duplicating the code would not be an ideal choice. However, as mentioned in the comments, you can make use of a repeater that loops over a grouped set of data (So you only query the database once), and then internally binds a GridView template.
The Aspx code could look like the following:
<asp:Repeater ID="repColors" OnItemDataBound="repColors_ItemDataBound" runat="server">
<ItemTemplate>
<asp:GridView ID="gvColor" runat="server" />
</ItemTemplate>
</asp:Repeater>
The Repeater has an OnItemDataBound that will be used to find and bind the GridView inside of its ItemTemplate. This GridView is simple, but could be as complex as you need it to be for your use case.
The aspx.cs page will contain the code you need to load all of your subjects into the repeater and then bind the gridview using the OnItemDataBound event handler.
protected void Page_Init(object sender, EventArgs e)
{
var data = GetColors();
var dataByColors = data.ToLookup(c => c.Subject, StringComparer.OrdinalIgnoreCase);
repColors.DataSource = dataByColors;
repColors.DataBind();
}
protected void repColors_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
var gv = e.Item.FindControl("gvColor") as GridView;
gv.DataSource = e.Item.DataItem;
gv.DataBind();
}
}
public class Colors
{
public string Text { get; set; }
public string Subject { get; set; }
}
private IEnumerable<Colors> GetColors()
{
yield return new Colors { Text = "Color1", Subject = "Blue" };
yield return new Colors { Text = "Color2", Subject = "Pink" };
yield return new Colors { Text = "Color3", Subject = "Blue" };
yield return new Colors { Text = "Color4", Subject = "Red" };
yield return new Colors { Text = "Color5", Subject = "Pink" };
}
Page_Load is used to fetch all of your data from the database. Then we use LINQ to group it by Subject which generates objects that look something like:
{"Blue": {Color1, Color3}}
{"Pink": {Color2, Color5}}
{"Red": {Color4}}
This is then bound to the repeater. The repeater's ItemDataBound event takes each individual data item (Which is a key and a list of colors) and binds it to the GridView that it's able to find in the Repeater template. The ILookup interface will by default enumerate over the list of items that it maintains. This allows it to be passed directly to the GridView.DataSource and we don't need to worry about trying to cast it to a List or anything.

ASP.NET Control Data Source changed by another Control

I have an ASP.NET Gridview control that allows you to select an employee.
The employee entity has a navigation property for group entity.
I have an ASP.NET ListView control that displays all the groups that an employee is in.
The SelectedIndexChanged function of the GridView looks like this
protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
{
DAL.SafetyContext sc = new DAL.SafetyContext();
long empid = (long)GridView1.SelectedDataKey.Value;
DAL.Employee emp = sc.Employees.Where(x => x.EID == empid).FirstOrDefault();
ListView1.DataSource = emp.Groups;
ListView1.DataBind();
}
The problem is that I can't <%#Eval("Name") %> in the item template of the ListView because there is no data bound to control when the page loads.
Is there a way around this?

Try creating an EmptyItemTemplate for your ListView. That way, when there is no data, you can display content that does not try to Eval on the (non-existent) "Name" data.
<EmptyItemTemplate>
<td runat="server">Nothing to see here</td>
</EmptyItemTemplate>
You can have it conform to the structure of your ItemTemplate, but just leave blanks / empty strings in all the places where you do databinding.

Dropdownlist first value display "choose"

I want that my dropdownlist display first value: "-choose car-"
I succeed at this way:
protected void ddl1_DataBound(object sender, EventArgs e)
{
Convert.ToInt32(ddl1.SelectedValue);
ddl1.Items.Insert(0, new ListItem("-Choose car-", "-Choose car-" ));
}
and that's ok,the "-choose-" is in the first place but the problem now is that if I have values,for example,the dropdownlist show like that:
-Choose car-
Subaro
Fiat
Honda
The first value that display when I'm enter to the site is the Subaro,and to see the -choose car- the user need to open the dropdownlist and then he will see the -choose car- at the first place.How can I do that from the start,from the page load - the -choose car- will display at the ddl from the page load.Where I wrong at the code ?
I tried the itemlist with AppendDataBoundItems = "true" but I got an error, and when I succeed,the problem is the same like I said before.

You were on the right track with using the AppendDataBoundItems property, it should be set to true if you're databinding the list.
Your markup should look like this
<asp:DropDownList runat="server" ID="ddl1" AppendDataBoundItems="true">
<asp:ListItem Text="-Choose car-" />
</asp:DropDownList>
and your code behind probably already looks something like this
ddl1.DataSource = [your datasource goes here];
ddl1.DataBind();
This will place the Choose car text as the first option in the drop-down list and append the rest of the options below it.
Now for the more interesting part of why you were seeing the behavior you were seeing (first item not being selected). If you look at the implementation of SelectedIndex using a tool like JustDecompile (not affiliated with Telerik, just happen to use their tool) you'll see code that looks like this:
public int SelectedIndex
{
get
{
int num = 0;
num++;
while (num < this.Items.Count)
{
if (this.Items[num].Selected)
{
return num;
}
}
return -1;
}
set
{
// stuff you don't care about
this.ClearSelection();
if (value >= 0)
{
this.Items[value].Selected = true;
}
// more stuff you don't care about
}
}
As you can see, the index isn't stored anywhere, it's computed every time based on which item has the Selected property set to true. When you set the SelectedIndex to 0 in the markup and databind your datasource, it will select the 0th item in that list, in your case Subaro. When you insert a new item at the beginning of the list, Subaro is still marked as the selected item, which is why when the page loads, you see that selected and not Choose car. If you want to mark Choose car as the selected item using code, you will have to do it after you data databind your dropdown. Please note, this is just an implementation detail of how DropdownList works. It could change in future version of ASP.NET so do not write code that relies on it working this way.

Make sure that you bind the data source and insert you "-choose care-" item first before selected he first item
make sure when you insert your 1st item "-Choose car-" you make it once not on each PostBack. Check if not IsPostBack to add the 1st item.
EDIT:
Example:
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
ddl1.Items.Insert(0, new ListItem("-Choose car-", "-Choose car-" ));
}
ddl1.SelectedIndex = 0;
}

You should do ddl1.Items.Insert(0, new ListItem("-Choose car-", "-Choose car-")); first, and than ddl1.SelectedIndex = 0

private void FillCar()
{
DataTable dt = GetCar();
ddl1.Items.Clear();
ddl1.DataSource = dt;
ddl1.DataTextField = "carName"; // field name in the database
ddl1.DataValueField = "CarNum"; // field name in the database
ddl1.DataBind();
ListItem li = new ListItem();
li.Text = "--Choose car--";
li.Value = "-1";
ddl1.Items.Insert(0, li);
ddl1.SelectedIndex = 0;
}
I use method like this and call it in the page load in if (!IsPostBack){}.

Dropdown gets cleared

I have one asp.net application, in which i have one dropdown which is binded to dataset. But after selecting one item, the drop down gets cleared all the value, How we can resolve this issue?
This is my dropdown list in design page:
<asp:DropDownList ID="ddlProduct" runat="server" CssClass="textEntry" Width="300px"
AutoPostBack="True" OnSelectedIndexChanged="ddlProduct_SelectedIndexChanged">
</asp:DropDownList>
and binding code is shown below.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
BindProductDdl();
}
private void BindProductDdl()
{
Products objProducts = new Products();
dsProducts dsProduct = new dsProducts();
ListItem olst = default(ListItem);
olst = new ListItem(" Select", "0");
dsProduct = objProducts.GetDataset("");
ddlProduct.DataSource = dsProduct;
ddlProduct.DataTextField = "Product";
ddlProduct.DataValueField = "Id";
ddlProduct.DataBind();
ddlProduct.Items.Insert(0, olst);
}
protected void ddlProduct_SelectedIndexChanged(object sender, EventArgs e)
{
Products objProducts = new Products();
dsProducts dsProduct = new dsProducts();
string criteria = "";
if (ddlProduct.SelectedItem.Text != " Select")
{
string id = ddlProduct.SelectedItem.Value;
criteria = "Id='" + id + "'";
dsProduct = objProducts.GetDataset(criteria);
productValue = Convert.ToDecimal(dsProduct.tblProducts.Rows[0]["Value"].ToString());
}
}
Thanks in advance..

From your question if I understand correctly you dont want the dropdown list to rebind if it is populated. Also please check your viewstate, this should not be happening, unless you have disabled viewstate
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack && ddlProduct.Items.count <=0 )
BindProductDdl();
}

Set the AppendDataBoundItems property of the dropdown to true and this will allow you to have a mix of databound items and non databound items (otherwise that insert statement is clearing your list)
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listcontrol.appenddatabounditems.aspx

Do you have viewstate disabled on the page? Since you are only loading the items into the dropdownlist on the first load of the page, if viewstate is not enabled there will be nothing in the list after the postback.

Not positive, but I've seen in other languages and false interpretation...
You have your product Value as convert of ToDecimal which implies 99.999 for example.
If your ID that you are binding to is based on a whole number (ie: Integer basis), the bound value won't match... even if Value = 1 vs Value = 1.00 it won't match and will not be considered a valid "value" that matches your list. Convert your answer to a whole/integer number and it might do what you expect.

Without seeing the full source for the page I am simply speculating, but have you disabled ViewState on the page? If so, the DropDownList cannot retain its values between postbacks and the lists will have to be reloaded each time.