How do I keep dynamically created dropdownlist when event OnSelectedIndexChanged?

[utterberg]

Hi

I'm adding two dropdownlist in my webform by clicking a button. I fill
the first dropdown with some values from my DB and the other one when I
choose from the first dropdown. But since theese dropdownlists are
created by clicking a button they no longer exists on my webform. How
do I keep my dynamically created dropdown when using
OnSelectedIndexChanged? Can anyone help me solve this problem? Or is
there a better way of doing this?

Thanks
..christer

(here's some of my code)
aspx-page:
<asp:Button Runat="server" ID="btnAddGroup" Text="Add Main-/Subgroup"
/>
<asplaceHolder ID="phGroup" Runat="server" /><asplaceHolder
ID="phSubGroup" Runat="server" />

code behinde (aspx.cs):
private void btnAddGroup_Click(object sender, System.EventArgs e){
CreateDropDown(this.phGroup, "selMainGrp");
}

private void CreateDropDown(PlaceHolder ph, string id){
DropDownList dd = new DropDownList();
FillMainGrpListBox(ph, dd, id);
}

private void FillMainGrpListBox(PlaceHolder ph, DropDownList dd, string
id){
DropDownList selMainGroup = dd;
string sqlProc = "GetMainGroup";

Data data = new Data();

resultDataSet = data.GetDataSetByProcName(sqlProc);

dd.Items.Add("Choose");

//Fill control
foreach(DataTable table in resultDataSet.Tables){
foreach(DataRow row in table.Rows){
foreach(DataColumn col in table.Columns){
//Add maingroup to dropdownlist
selMainGroup.Items.Add(row[col].ToString());
}
}
}

//Add control
string sAttributes;
sAttributes = "<b>Main Group</b>";
ph.Controls.Add(new LiteralControl(sAttributes));
selMainGroup.ID = id;
selMainGroup.AutoPostBack = true;
selMainGroup.SelectedIndexChanged +=new
EventHandler(selMainGroup_SelectedIndexChanged);
ph.Controls.Add(selMainGroup);

//Add Subgroup dropdown
DropDownList ddSub = new DropDownList();
sAttributes = "<b>Sub group</b>";
ddSub.ID = "selSubGrp";
ddSub.Items.Add("Choose");
phSubGroup.Controls.Add(new LiteralControl(sAttributes));
phSubGroup.Controls.Add(ddSub);
}

private void selMainGroup_SelectedIndexChanged(object sender,
System.EventArgs e){
string mainGroupValue = this.selMainGrp.SelectedValue;
if(mainGroupValue != "Choose"){
//Reset subgroup dropdown
SetDefaultListBoxValue(selSubGrp);

//Add values in subgroup
FillSubGrpListBox(mainGroupValue);
}
}

private void FillSubGrpListBox(string mainGroupValue){
string sqlProc = "GetSubGroup";

string[,] paramArr = {{"@MainGroup",mainGroupValue}};

Data data = new Data();
resultDataSet = data.GetDataSetByProcName(sqlProc, paramArr);

foreach(DataTable table in resultDataSet.Tables){
foreach(DataRow row in table.Rows){
foreach(DataColumn col in table.Columns){
selSubGrp.Items.Add(row[col].ToString());
}
}
}
}

 

[utterberg]

What I want to do is click on my "Add"-button and create two dropdowns
- the first I fill with values from my DB. Then I select a value from
the first drop down and fill the other drop down (with another
roundtrip to my DB collecting the new values for the second dropdown).
When that's done I want to click my "Add Selection"-button and add the
selection to my webform (values from both dropdowns). After that I
would like to add another dropdown make my selection and and add it to
my webform, and so on.

When I've made all my selections I would like to press a "Save"-button
and save all the selected values to my DB.

Thus, I do not know in advance how many selections I would like to make
and thats why I wanna create theese controls at run time.

Hope this clarified a bit
..christer

 

[Eliyahu Goldin]

Instead of creating the ddls dynamically, put them on the .aspx form in a
normal way and, in run time, control their visibility and databinding
properties.

Eliyahu

Hi

I'm adding two dropdownlist in my webform by clicking a button. I fill
the first dropdown with some values from my DB and the other one when I
choose from the first dropdown. But since theese dropdownlists are
created by clicking a button they no longer exists on my webform. How
do I keep my dynamically created dropdown when using
OnSelectedIndexChanged? Can anyone help me solve this problem? Or is
there a better way of doing this?

Thanks
.christer

(here's some of my code)
aspx-page:
<asp:Button Runat="server" ID="btnAddGroup" Text="Add Main-/Subgroup"
/>
<asplaceHolder ID="phGroup" Runat="server" /><asplaceHolder
ID="phSubGroup" Runat="server" />

code behinde (aspx.cs):
private void btnAddGroup_Click(object sender, System.EventArgs e){
CreateDropDown(this.phGroup, "selMainGrp");
}

private void CreateDropDown(PlaceHolder ph, string id){
DropDownList dd = new DropDownList();
FillMainGrpListBox(ph, dd, id);
}

private void FillMainGrpListBox(PlaceHolder ph, DropDownList dd, string
id){
DropDownList selMainGroup = dd;
string sqlProc = "GetMainGroup";

Data data = new Data();

resultDataSet = data.GetDataSetByProcName(sqlProc);

dd.Items.Add("Choose");

//Fill control
foreach(DataTable table in resultDataSet.Tables){
foreach(DataRow row in table.Rows){
foreach(DataColumn col in table.Columns){
//Add maingroup to dropdownlist
selMainGroup.Items.Add(row[col].ToString());
}
}
}

//Add control
string sAttributes;
sAttributes = "<b>Main Group</b>";
ph.Controls.Add(new LiteralControl(sAttributes));
selMainGroup.ID = id;
selMainGroup.AutoPostBack = true;
selMainGroup.SelectedIndexChanged +=new
EventHandler(selMainGroup_SelectedIndexChanged);
ph.Controls.Add(selMainGroup);

//Add Subgroup dropdown
DropDownList ddSub = new DropDownList();
sAttributes = "<b>Sub group</b>";
ddSub.ID = "selSubGrp";
ddSub.Items.Add("Choose");
phSubGroup.Controls.Add(new LiteralControl(sAttributes));
phSubGroup.Controls.Add(ddSub);
}

private void selMainGroup_SelectedIndexChanged(object sender,
System.EventArgs e){
string mainGroupValue = this.selMainGrp.SelectedValue;
if(mainGroupValue != "Choose"){
//Reset subgroup dropdown
SetDefaultListBoxValue(selSubGrp);

//Add values in subgroup
FillSubGrpListBox(mainGroupValue);
}
}

private void FillSubGrpListBox(string mainGroupValue){
string sqlProc = "GetSubGroup";

string[,] paramArr = {{"@MainGroup",mainGroupValue}};

Data data = new Data();
resultDataSet = data.GetDataSetByProcName(sqlProc, paramArr);

foreach(DataTable table in resultDataSet.Tables){
foreach(DataRow row in table.Rows){
foreach(DataColumn col in table.Columns){
selSubGrp.Items.Add(row[col].ToString());
}
}
}
}

 

[Eliyahu Goldin]

Do you mean that first "Add" click produces 2 ddls, then another "Add"
produces another 2 ddls and you will have 4 ddls on the form? And 6 ddls
after the third click?

Can't you use the same pair of ddls for every "Add" click?

Eliyahu

 

[utterberg]

Ok. But how do I preserve (and view) the value when I click my "Add
selection"-button?

If I use a <asplaceholder ../> for instance and try to place my drop
down values in that place when clicking "Add selection" the page
reloads and selection (value) is gone.

..christer

 

[utterberg]

I am lousy at explaining I think. And my english ain't what it should
be.

I want to preserve/add values in a placeholder when I make my
selection. I can do this with my first dd selection like this.
- Make my selection in my drop down
- Add selection to a placeholder by clicking "btnAddSales"

aspx:
<label for="selSalesAccount">Sales Account:</label>
<aspropDownList Runat="server" ID="selSalesAccount"
AutoPostBack="True" />
<asp:Button Runat="server" ID="btnAddSales" />
<asplaceHolder Runat="server" ID="phSales" />

code behind:
private void btnAddSales_Click(object sender, EventArgs e){
string val = this.selSalesAccount.SelectedValue;
TextBox tb = new TextBox();
tb.ID = val;
this.phSales.Controls.Add(tb);
tb.Text = val;
tb.AutoPostBack = true;
}

So now I have my first drop down selection in my placeholder. Now I
want to make another selection from my dropdown and add its value to my
placeholder (making it two values) - but when I choose a new item in
the drop down values preserved in my placeholder is gone.

How do I keep thees selected values when I do another runtrip to the
server?

(this is a simplyfied example of what I want to do, but if I can get
help with this I should be able to sort the rest out myself)

..christer

 

[Eliyahu Goldin]

If you have 2 static ddls, what stops you from getting their selected values
on server side in the "Add selection" onclick event handler?

Eliyahu

 

[Eliyahu Goldin]

A placeholder is not good for you. First of all, choose a class you want to
use to store the selection. It could be an array, ArrayList, SortedList,
DataTable. Secondly, decide on how to make it persistent between the
postbacks. You can put it in a session variable or in the ViewState. Then
finally chose a web control that will render your selection on the page.
Typically it would be a datagrid, a datalist or a repeater. And finally bind
your control to your storage object on every postback.

Eliyahu

 

[utterberg]

Ok thanks!
I'll try that.

..christer