Develop Reference

dropdown selected item and repose.redirect

I have two dropdownlist in my project and get the items from sql server. One of them show list of something (And I named it DropdownSoore) and another one show list of members of it (And I named it DropdownAye) that update when select an item from DropdownSoore. then when select an item from DropdownAye go to page of them by forwarding query string. I have no problem to updating DropdownAye but when I select item from it and redirect to page of it, the DropdownAye lose the selected item and show the first item (as default) and index to query string in url.
what should I do?
Excuse me about my grammer, I'm not English...
I set DropdownSoore:
<asp:DropDownList ID="DropDownListSoore" runat="server" class="nav-link btn btn-outline-secondary dropdown-toggle" aria-haspopup="true" aria-expanded="true" AutoPostBack="True"></asp:DropDownList>
for (int i = 0; i <= dt.Rows.Count - 1; i++)
{
string IdSoore = Convert.ToString(dt.Rows[i]["IdSoore"]);
string NameSoore = Convert.ToString(dt.Rows[i]["NameSoore"]);
DropDownListSoore.Items.Add(IdSoore + "." + NameSoore);
}
string forwardedIdSoore = Request.QueryString["IdSoore"];
if (forwardedIdSoore != null)
{
DropDownListSoore.Items.FindByValue(forwardedIdSoore);
}
And then set DropdownAye:
<asp:DropDownList ID="DropDownListAye" runat="server" class="nav-link btn btn-outline-secondary dropdown-toggle" aria-haspopup="true" aria-expanded="true" OnSelectedIndexChanged="DropDownListAye_SelectedIndexChanged" AutoPostBack="True"></asp:DropDownList>
DropDownListAye.Items.Clear();
for (int i = 0; i <= dt1.Rows.Count - 1; i++)
{
DropDownListAye.Items.Add(Convert.ToString(dt1.Rows[i]["NumberAye"]));
}
int iSelectedAye = Convert.ToInt32(DropDownListAye.SelectedIndex) + 1;
string SelectedAye = Convert.ToString(dt1.Rows[iSelectedAye]["IdAye"]);
Session["SSelectedAye"] = SelectedAye;
string forwardedIdAye = Request.QueryString["IdAye"];
if (forwardedIdSoore != null)
{
DropDownListSoore.Items.FindByValue(forwardedIdAye);
}
in page_Load. and dont have problem to update DopdownAye but when I used it to redirect always get IdAye=1 in url and show the first item of DropdownAye ...:
protected void DropDownListAye_SelectedIndexChanged(object sender, EventArgs e)
{
int SelectedAye = Convert.ToInt32(Session["SSelectedAye"]);
int SelectedSoore = Convert.ToInt32(DropDownListSoore.SelectedIndex) + 1;
string forward = "~/contentAye.aspx?IdSoore=" + SelectedSoore + "&IdAye=" + SelectedAye;
Response.Redirect(forward);
}
I try !IsPostBack but dont have utility too.
I do all thing I think and i dont know what shoild i do.

And where are you loading up these infomration?
Remember, page load ALWAYS fires and triggers for each post-back, for each button click, and any OTHER event on the page that calls code behind.
What does the above really mean?
Well, it means that you need to ONLY ONE TIME load up the drop downs, the gridview(s), or whatever else you have.
So, for the last 200+ web pages I have built, I ALWAYS have this code stub in the page load event:
so this markup:
<h3>Select Hotel</h3>
<asp:DropDownList ID="DropDownList1" runat="server"
DataValueField="ID"
DataTextField="HotelName" Width="356px">
</asp:DropDownList>
<br />
<br />
<asp:Button ID="Button1" runat="server"
Text="Show/get/display drop selection" OnClick="Button1_Click"
CssClass="btn" />
<br />
<h3>Selected result</h3>
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>
and code behind:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
// load up data, controls etc.
string strSQL =
"SELECT ID, HotelName FROM tblHotelsA ORDER BY HotelName";
DataTable dt = General.MyRst(strSQL);
DropDownList1.DataSource = dt;
DropDownList1.DataBind();
DropDownList1.Items.Insert(0, new ListItem("Please Select Hotel", ""));
}
}
protected void Button1_Click(object sender, EventArgs e)
{
string sResault =
$#"dropdown list value (pkid) = {DropDownList1.SelectedItem.Value}
<br/>
Dropdown list Text (Hotel) = {DropDownList1.SelectedItem.Text}";
Label1.Text = sResault;
}
and the result:
SUPER important:
If I leave out the !IsPostBack test in page load, then for EVERY button click, the dropdown list re-load code will trigger, and runs BEFORE your button stubb, or post back. As a result, I will see/find/get no valid value from the drop down list, since page load ALWAYS runs before the given code stub, and thus if page load "every time" re-loads the data, then it will blow out the choosen value in the drop down list.
So, loading up of grids, data, dropdowns etc. can ONLY occur one time in page load, since page load ALWAYS runs before each button or event code stub you have behind.
If you thus only load up the controls and dropdowns on the first REAL page load, then the values the user selects in those dropdowns should work, but only will work if you ALWAYS include that all important if (!IsPostBack) code stub in your page load event.
Now, of course in place of that button to loadup + display the dropdown list into that label?
Well, of course that button click may well (like often) jump or navigate to another page. So, in place of that code to fill out the selected value(s) into that lable, we could pass the selected value to the next page. And how to do that? Well, you can use session(), you can use parmaters in the URL, or you can even use a post-back URL, and then the WHOLE previous page becomes available (Page.Previous), which then in theory allows you to grab ANY and ALL values from the previous page.
but, say we choose session() to pass the value, then this:
Session["HotelPK"] = DropDownList1.SelectedItem.Value;
Response.Redirect("GridFun3.aspx");

Datagrid ItemCommand event not firing

I am still a novice with asp.net, so I'm sure there are better ways to do some of this...
I want to allow a user to enter a date, and then execute an SQL query against a database to return all records matching that date. I want to display those records, and allow the user to select one for additional processing. It seemed like the DataGrid with a column of Pushbuttons was a good choice. In fact, I've done this before, but it those cases there was no user interaction involved. The page just ran a fixed SQL query. With what I'm doing now, the data is displayed as I want, but the Pushbuttons aren't working...the ItemCommand event doesn't fire.
I've read a lot of threads about the ItemCommand event not firing, but I still can't get this to work. My understanding is that I need to bind the DataGrid while not in a Postback, and I think my code does that. When I debug the Page_Load event, I can see that the code inside if (!IsPostBack){} is running, and the session variables have the expected data.
On the page that hosts the DataGrid, I have a 'Find' button that executes a SQL query against a database. The query uses a date entered into the textbox that is on that page. In the 'Find' button click event, I store the results of the query (a DataTable) in a session variable, then do a Redirect to re-load the page.
Once the page reloads, the session variables contain my expected data and the data is displayed in the DataGrid, along with the Pushbuttons. When I click any of the buttons in the DataGrid, the contents of the DataGrid disappear and the ItemCommand event does not fire.
Here's the definition of the DataGrid (updated to include the button):
<asp:Panel runat="server" ID="pnlSelect" HorizontalAlign="Left" Visible="true" style="margin-top:10px" >
Please select a participant.
<asp:DataGrid runat="server" ID="grdItems" AutoGenerateColumns="true" BorderColor="black" BorderWidth="1" CellPadding="3" style="margin-left:2px; margin-top:6px" OnItemCommand="grdSelect_ItemCommand" >
<Columns>
<asp:ButtonColumn HeaderStyle-HorizontalAlign="Center" ButtonType="PushButton" Text="Select" HeaderText="Select" CommandName="Select" >
<ItemStyle Width="60px" HorizontalAlign="Center"/>
</asp:ButtonColumn>
</Columns>
</asp:DataGrid>
</asp:Panel>
Here's the Page Load code (unneeded code-behind stuff is commented out):
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
if (Session["y"] != null)
{
txtFind.Text = Session["x"].ToString();
DataTable table = Session["y"] as DataTable;
Session.Remove("x");
Session.Remove("y");
if (table != null)
{
/*
ButtonColumn buttonColumn = new ButtonColumn
{
HeaderText = "Select",
Text = "Select",
CommandName = "Select",
ButtonType = ButtonColumnType.PushButton,
};
grdItems.Columns.Add(buttonColumn);
foreach (DataColumn c in table.Columns)
{
BoundColumn column = new BoundColumn
{
HeaderText = c.Caption,
DataField = c.Caption,
ReadOnly = true
};
grdItems.Columns.Add(column);
}
*/
grdItems.DataSource = table;
grdItems.DataBind();
}
}
}
}
Here's the relevant 'Find' button event code. I can't post the details of the sql query text, but that part does work and the DataTable does contain the expected data:
DataTable table = DatabaseHelper.FindBySQL(sqlText);
if (table != null && table.Rows.Count > 0)
{
Session["x"] = searchtext;
Session["y"] = table;
Response.Redirect(Request.RawUrl, true);
}
And this the ItemCommand event. I place a breakpoint on the first line, and the debugger never hits it.
protected void grdItems_ItemCommand(object source, DataGridCommandEventArgs e)
{
string item = "";
switch (e.CommandName.ToLower())
{
case "select":
item = e.Item.Cells[1].Text.Trim();
//todo: handle the selected data
break;
}
}
Thanks for any thoughts.
Don

ASP table row count not getting incremented

I have an ASP table, with a dropdownlist and text box in its 1st row. I have a button on click of which a similar row should be added. I have the following function in its button click event.
public void addRow()
{
int flag = Table1.Rows.Count;
DropDownList ddl = new DropDownList();
ddl.ID = "ddl" + (flag + 1).ToString();
TextBox tBox = new TextBox();
tBox.ID = "txt" + (flag + 1).ToString();
TableCell tCell1 = new TableCell();
TableCell tCell2 = new TableCell();
tCell1.Controls.Add(ddl);
tCell2.Controls.Add(tBox);
TableRow tRow = new TableRow();
tRow.Cells.Add(tCell1);
tRow.Cells.Add(tCell2);
Table1.Rows.Add(tRow);
}
This code works fine when adding 2nd row. When I click the button again, the value of flag which should have the value of number of rows of the table is not getting incremented. So a new row doesn't get created. Can you please tell me why the value of flag doesn't get incremented ? Or is their an easier way to do this ? Direct answer or link would be helpful.
Mark up code for Table:
<asp:Table ID="Table1" runat="server" Width="410px">
<asp:TableRow>
<asp:TableCell>
<asp:DropDownList runat="server" ID="ddl1"></asp:DropDownList>
</asp:TableCell>
<asp:TableCell>
<asp:TextBox runat="server" ID="txt1"></asp:TextBox>
</asp:TableCell>
</asp:TableRow>
</asp:Table>

Warning - Big ugly block of text
I'm going to try and explain why what you're trying to do is not as simple as it sounds (or as simple as I'd like it to be) and hopfully give you an alterantive approach, which while it
may not be straight forward, it should be "better".
It looks a high level overview of what you are trying to do is the following:
Give the user the oppotunity to add one or more records to a collection (database) before finalising the save.
It is possible to do this using postback to generate the additional rows/items beofore clicking the final save button. Hover this may not be the easiest, or best, way to do this.
From a technical viewpoint adding dynamic controls has to be handeld in a very specific manner at a specific point in the ASP.net page lifecylce. Dynamic controls also have to be recreated on every post back, so every time a user clicks the "add" button, you will have to re-reate the rows you already have in addition to the new row. This is why you only get the one row in this example. Thats just the adding of the dynaimc controls. Wait till you get to getting data from your dynamic text boxes and drop downs!
From an end users perspective, this approach is also not ideal as every time the user clicks the "add" button the page cycles through the request/response process, which at the minumun cuases a bit of an ugly flash.
Update
But how? I hear you ask. Well here it is (I've simplified it to one column for this example):
ASPX
<asp:Table ID="Table1" runat="server">
<asp:TableRow>
<asp:TableCell><asp:TextBox ID="txt1" runat="server"> </asp:TextBox></asp:TableCell>
</asp:TableRow>
</asp:Table>
<asp:Button ID="btnAdd" runat="server" Text="Add" onclick="Button1_Click" />
<asp:HiddenField ID="hdnRowCount" runat="server" />
<asp:Button ID="btnSave" runat="server" onclick="btnSave_Click" Text="Save" />
<div>
<asp:Label ID="lblResult" runat="server" Visible="false"></asp:Label>
</div>
C#
private int rowCount = 1;
private bool rowNeeded = false;
protected override void OnPreInit(EventArgs e)
{
//Pre-emptively create additional row on post back.
//We'll remove it if we don't need it later
//Controls Have to be added at pre-init to maintain their view state
//Adding a row in the button click event will result in any data
//entered in that row dissapearing from viewstate on next post back
if (IsPostBack)
{
//Get number of additional rows from hidden field
//We're using a hidden form field and Request.Form
//instead of ViewsState and hdnRowCount.value
//because ViewState has not been loaded at this stage
//of the page life cycle
if (!string.IsNullOrEmpty(Request.Form["hdnRowCount"]))
{
rowCount = int.Parse(Request.Form["hdnRowCount"]);
}
for (int i = 0; i < rowCount; i++)
{
TableRow tr = new TableRow();
TableCell tc = new TableCell();
TextBox tb = new TextBox();
// +2 as there are existing controls with "1", eg txt1
tb.ID = string.Format("txt{0}",i+2);
tc.Controls.Add(tb);
tr.Cells.Add(tc);
Table1.Rows.Add(tr);
}
}
base.OnPreInit(e);
}
//Add Row Click
protected void Button1_Click(object sender, EventArgs e)
{
//Hold number of additional rows in hidne field
hdnRowCount.Value = (++rowCount).ToString();
//Let the page know we need to keep the row
rowNeeded = true;
}
//An Exmple of how to get your data out
protected void btnSave_Click(object sender, EventArgs e)
{
string s = "";
//Iterate through the table rows finding the controls
//Using count -1 as we still have the pre-emptive row
for(int i = 0; i < Table1.Rows.Count-1; i++)
{
TextBox tb = (TextBox)Table1.Rows[i].FindControl(string.Format("txt{0}",i+1));
s += "," + tb.Text;
}
lblResult.Text = s;
lblResult.Visible = true;
}
protected override void OnLoadComplete(EventArgs e)
{
//Get rid of pre-emptive row if we don't need it
if (IsPostBack)
{
if (!rowNeeded)
{
Table1.Rows.RemoveAt(Table1.Rows.Count - 1);
}
}
base.OnLoadComplete(e);
}
End Update
So, how would I do it? Client side, is the answer to that question. I would use jQuery to create a clone of the first row. You then would need to adjust the id and name attributes of your form fields before appending your new row to the table. You would also need a hidden form field to keep track of the number of hidden rows. When your user finaly hits the "save" button, on the C# side, get the number of additional rows from you hidden field the go old school and use Request.Form[] to get the value of each of your added fields.
This, in my opionion, will be a smoother experience for the end user.
Another, somewhat hacky option,if you have a defined maximum number of additional rows. For this have the mamimum rows, with form controls in the table. You can then either use visible="false" in the aspx and use post back to change that to visible="true" when the user clicks "add". The other option there is to give the row a CSS class that hides the row and then use javascript/jquery to remove the class to make the row visible.

The issue here is that you are not understanding the ASP.Net Page Lifecycle and more importantly how it interacts with dynamic controls (your added controls.)
Unfortunately, we can not answer this question without understanding whether the values in these "dynamically" created controls are used server-side or client-side.
I can guess that:
1) If they are for client side consumption/usage, you are doing wrong. If you need more info ask another (more specific) question.
2) If they are for server side consumption/usage, you must only allow one new record per postback, and should include a "Save" button that will save the current "new" row and cause a page refresh that the user can add a new entry to.
3) See rule #0 (Every rule has exceptions. {This rule applies in so far that you understand the problem at hand.})
Monk

Is it possible to programmatically input values in TextBox control before UpdateCommand runs

(C# asp.net 3.5) I have successfully pre-populated CheckBoxList3 in RowDataBound event. In edit mode, user may then make other checkbox selections. I have successfully captured the new values, creating a new comma-delimited string that updates SQL in _RowUpdating event after Update link is clicked. The problem is my update is being overriden by the GridView1s update. *The new string is not physically input by user in the TextBox2 control.
It seems I have two choices:
Pass the comma-delimited string built from checkboxlist3 selections
to TextBox2 control programmatically before UpdateCommand is run. P*Is this possible?* I've
googled everywhere with no clearcut solutions. I've also tried this code in RowUpdating and it makes to difference:
TextBox tb2 = (TextBox)GridView1.Rows[e.RowIndex].Cells[1].FindControl("TextBox2");
tb2.Text = strCheckBoxList3.Substring(0, strCheckBoxList3.Length - 2);
Update sql manually like I'm doing only place Sql call AFTER the "natural" update (for lack of
better words). If this is an option, what method to run the update in because placing it in RowUpdating always gets reversed.
HTML:
<asp:TemplateField HeaderText="Endorsements" SortExpression="Endorsements">
<ItemTemplate>
<asp:Label ID="Label2" runat="server" Text='<%# Bind("Endorsements") %>'></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("Endorsements") %>'></asp:TextBox>
<asp:CheckBoxList ID="CheckBoxList3" runat="server" Font-Size="Small" RepeatDirection="Horizontal" onselectedindexchanged="CheckBoxList3_SelectedIndexChanged"
AutoPostBack="True" >
<asp:ListItem Value="H">H</asp:ListItem>
<asp:ListItem Value="I">I</asp:ListItem>
<asp:ListItem Value="K">K</asp:ListItem>
<asp:ListItem Value="N">N</asp:ListItem>
<asp:ListItem Value="T">T</asp:ListItem>
<asp:ListItem Value="X">X</asp:ListItem>
</asp:CheckBoxList>
</EditItemTemplate>
</asp:TemplateField>
C#
protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
//endorsements string
string strCheckBoxList3 = String.Empty;
//find endorsements checkboxlist in gridview.
CheckBoxList cbl3 = (CheckBoxList)GridView1.Rows[e.RowIndex].Cells[1].FindControl("CheckBoxList3");
try
{
// Build Endorsements string
if (cbl3 != null)
{
// determine which checkboxes have been checked
foreach (ListItem item in cbl3.Items)
{
// is item checked?
if (item.Selected == true)
{
// build string
strCheckBoxList3 += (item.Value + ", ");
}//end of if
}// end of foreach
// Save the value in ViewState object before the PostBack
ViewState["vsEndorsementsString"] = strCheckBoxList3;
}// end of if
}// end of endorsements try
catch (ArgumentOutOfRangeException ez)
{
System.Diagnostics.Debug.WriteLine(ez.Message + "; " + ez.Source + "; " + ez.TargetSite);
}
//Note: routine to update SQL was removed here
}
// New: pass strings to sql Update Command Parameters for two checkboxlist columns in gridview
protected void sdsMySqlDataSource_Updating(object sender, SqlDataSourceCommandEventArgs e)
{
string getViewStateEndorsementsString = ViewState["vsEndorsementsString"].ToString();
string getViewStateRestrictionsString = ViewState["vsRestrictionsString"].ToString();
foreach (System.Data.Common.DbParameter p in e.Command.Parameters)
{
if (p.ParameterName == "#Endorsements" && p.Value != null)
{
//Assign #Endorsements parameter
e.Command.Parameters["#Endorsements"].Value = getViewStateEndorsementsString.ToString();
}//if
if (p.ParameterName == "#Restrictions" && p.Value != null)
{
//Assign #Restrictions parameter
e.Command.Parameters["#Restrictions"].Value = getViewStateRestrictionsString.ToString();
}//if
}
}

The solution is to pass new values to Update Command Parameters in SqlDataSource _Updating event. Relevent updated code provided above.
I removed the SQL update routine that I had in _RowUpdating event entirely - it isn't needed. Then I saved the newly created comma-delimited string to ViewState object which I retrieve in SqlDataSource _Updating event.
Credit for me coming to this conclusion goes to leoinlios because of his post here: changing textbox value in code behind does not post back new value Plus I did a lot of reading about View State and found this to be the most useful article: TRULY Understanding ViewState

DropDown Selected Value not Showing up

I have drop-down inside of a gridview so when the gridview is loaded and the drop-down is bound then the drop-down only show the first value of the drop-down list and it is not showing the previously selected value. When the gridview loads, i would like the drop-down to show what was previously selected for that row. Here is my code:
aspx markup for the drop-down:
<asp:TemplateField HeaderText="Answer">
<ItemTemplate>
<asp:Label ID="lblAns" runat="server" Text='<%# Eval("DDL_ANS")%>' Visible="false"></asp:Label>
<asp:DropDownList ID="ddl_Answer" runat="server">
</asp:DropDownList>
</ItemTemplate>
Here is code behind:
protected void RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
DropDownList ddl_Answer;
//get current index selected
int current_quest = Convert.ToInt32(GridView1.DataKeys[e.Row.RowIndex].Value);
ddl_Answer = e.Row.FindControl("ddl_Answer") as DropDownList;
using (SqlConnection con2 = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["myconnection"].ConnectionString))
{
con2.Open();
using (SqlCommand cmd1 = new SqlCommand("select distinct DD_ANSWER from table1 where ID= '" + current_quest + "' ", con2))
{
ddl_Answer.DataSource = cmd1.ExecuteReader();
ddl_Answer.DataTextField = "DD_ANSWER";
ddl_Answer.DataValueField = "DD_ANSWER";
ddl_Answer.DataBind();
}
con2.Close();
}
}
I have tried to add this line of code after binding but i get this error "Object reference not set to an instance of an object"
ddl_Answer.Items.FindByValue((e.Row.FindControl("lblAns") as Label).Text).Selected = true;
thanks

I believe in your SELECT you need to use current_quest_sk instead of current_quest
Aslo try to check for null before accessing your controls:
var ddl_Answer = e.Row.FindControl("ddl_Answer") as DropDownList;
var answerLabel = e.Row.FindControl("lblAns") as Label;
if(answerLabel !=null && ddl_Answer!=null)
{
ddl_Answer.Items.FindByValue(answerLabel.Text).Selected = true;
}
#afzalulh has a valid point remove quotes if current_quest_sk(ID) is an Integer in your table.
You should avoid SQL injection but that's a different topic.

Place a breakpoint in your code, and setup through it with your debugger.
Either you have a typo in one of your string names or you are looking at the wrong control.
Stepping through your code will help you see exactly what line of your code is causing the problem.
You could also put a try/catch block around the whole thing to help you isolate the problem. Once you find the problem, remove the try/catch block.