After doing a lot of research online I'm still stumped by this problem. I have a page that loads the names and count of categories into a drop down list. I only do this if !(Page.IsPostBack). When AutoPostBack fires the SelectedIndex = 0. I've tried several different things. Here is my code:
PAGE
<form id="AddAssignmentForm" runat="server">
<asp:ScriptManager ID="ScriptManager1" EnablePartialRendering="true" runat="server" />
<asp:UpdatePanel ID="CommentUpdate" runat="server">
<ContentTemplate>
Add Comment
<asp:DropDownList ID="ddlCategory" runat="server" Width="206" OnSelectedIndexChanged="ddlCategory_SelectedIndexChanged" AutoPostBack="true" />
<asp:TextBox ID="txtName" runat="server" Width="200" />
<asp:TextBox ID="txtAbbrv" runat="server" Width="200" />
<asp:TextBox ID="txtDescription" runat="server" Width="200" Height="90" TextMode="MultiLine" />
</ContentTemplate>
</asp:UpdatePanel>
</form>
Here is the back end code.
private void Page_Load(object sender, System.EventArgs e)
{
if (!Page.IsPostBack)
{
GetCategories();
}
}
public void GetCategories()
{
String strSql = #"SELECT Name, Total
FROM MyTable";
if (con.State == ConnectionState.Closed)
con.Open();
OleDbCommand cmdsql = new OleDbCommand(strSql, con);
OleDbDataReader cmdReader = cmdsql.ExecuteReader();
if (cmdReader.HasRows)
{
while (cmdReader.Read())
{
ddlCategory.Items.Add(new ListItem(cmdReader["Category_Name"].ToString(), cmdReader["Total"].ToString()));
}
ddlCategory.SelectedIndex = -1;
}
cmdReader.Close();
con.Close();
}
public void FillForm(int index)
{
ListItem item = ddlCategory.Items[index];
txtName.Text = item.Text + " " + (Convert.ToInt32(item.Value) + 1).ToString();
txtAbbrv.Text = item.Text.Substring(0, 1) + (Convert.ToInt32(item.Value) + 1).ToString();
}
public void ddlCategory_SelectedIndexChanged(Object sender, EventArgs e)
{
//When I break here SelectedIndex always = 1.
FillForm(ddlCategory.SelectedIndex);
}
I just want to be able to populate the form based on the selected index, but I can't seem to get the correct answer. Any help is appreciated.
Add AppendDataBoundItems="true" for dropdown list
I discovered the problem. The values being populated from my SQL statement contained values that repeated. For some reason this was causing the entire thing to malfunction in weird ways which made it so that every time I selected a ListItem the whole list would reset. By making sure no values repeated, the code started working perfectly. Thanks for everyone's help.
Make sure that your value fields are unique for each dropdown list item. If each item has the same value, it will default on index 0.
Do you have Viewstate enabled or disabled? SelectedIndex is Zero based, so it were resetting I think it would be set to zero.
Also, what do the other properties of the drop down list get set to? Is the selected value correct?
Try a different browser. I had an issue with cascading drop downs where it wasn't firing/behaving correctly in Firefox.
This happened to me when attempting to use a combined column value for the DataValueField. For example:
The stored procedure was written like this:
SELECT
Description,
Value1 + ',' + Value2 AS Value
FROM
DropDownListTable
And the DataValueField used the Value field which was a combination of the Value1 and Value2 fields separated by a comma. (I also tried a pipe and no delimiter but had the same results)
With ddl
.DataTextField = "Description"
.DataValueField = "Value"
.DataSource = ds
.DataBind()
End With
As soon as I used Value1 or Value2 as the DataValueField, the problem went away.
I struggled with this too, I tried EnableViewState="true" ViewStateMode="Enabled" but it's not needed in fact, you just have to addd IsPostBack in Page_Load event.
Do not forget to add IsPostBack, that is it...
if (!IsPostBack)
{
LoadDropDown();
}
You have to load list to DropDownList if not IsPostBack
Example code:
if (!IsPostBack)
{
//fill here
}
I've been experiencing the same problem, my dropdownlist stateview jump to index 1 right after a postback event from another control. My suggestion simply make sure your dropdownlist values are not empty.
Hope its help someone .... :)
Related
So I create a button in the behind code using a function in an Repeater. And then, there's a button that should take these automatically generated buttons (if I check the checkbox in button A, I take the values of row A in repeater,same goes for button B and so on...).
I can see checking the code while debugging that the checkbox are generated correctly. So I should just be able to find it, but can not. Even tho I use the findControl but have not been able to do it.
Here is the code from the front:
<asp:Panel ID="mainPanel" runat="server">
<asp:Repeater ID="repStudents" runat="server">
....
<%# GetButton(Eval("Role").ToString()) %>
....
<asp:LinkButton runat="server" OnClick="showChosen" ClientIDMode="Static"
CausesValidation="true">Save</asp:LinkButton>
And here I generate the button and then try to show the chosen value:
protected string GetButton(string status)
{
string love="";
if(status == "Rel")
{
love = "<input id='relBtn' type='checkbox' runat='server'/>";
}
else
{
love = "<input id='rfBtn' checked type='checkbox' runat='server'/>";
}
return love;
}
protected void showChosen(object sender, EventArgs e)
{
CheckBox cb = (CheckBox)(mainPanel.FindControl("relBtn"));
if(cb.Checked)
lblError.Text = "Checkbox is checked";
else
lblError.Text = "Checkbox is not checked";
divError.Visible = true;
All I keep getting is the Null Reference Exception, even tho, there is just one relBtn in the whole page. If I look into the page generated code, I can see the relBtn, but for some reason, I can not find the Checkbox.
Ok, unless you crossed the desert, climbed mountains, exhausted every "reasonable" alternative?
You have to ask WHY you want to write code to inject a button when THAT is the WHOLE idea of quite near EVERY control from repeater, listview, Gridview and more!
In other words, the need for writing code code, and a GOOD strong case has not been made yet.
and why do we need a huge spectacular earth shaking narrative as to why the approach is being used?
Because in 99% of cases, you don't need to do this, and the data aware controls and darn near the WHOLE asp.net system is designed around you NOT having to take that road.
So, if you have some button, or whatever? Just drop it into the repeater control, and it will "repeat" over and over for you!!!
So, say this simple repeater:
<asp:Repeater ID="Repeater1" runat="server" >
<ItemTemplate>
<div style="border-style:solid;color:black;width:320px;height:450px;float:left;margin-right:10px;margin-bottom:10px">
<div style="text-align:center;padding:2px 10px 2px 10px" class="cards" >
<asp:Button ID="cmdMyView" runat="server" Text="View"
CssClass="btn-info" style="float:right"
CommandArgument = '<%# Eval("ID") %>'
OnClick="cmdMyView_Click" />
<br />
<h3 id="hFighter" runat="server"><%# Eval("Fighter") %></h3>
<asp:Image ID="Image2" runat="server"
ImageUrl = '<%# Eval("ImagePath") %>' Width="170" />
<h4>Engine</h4>
<asp:Label ID="EngineLabel2" runat="server" Text='<%# Eval("Engine") %>' />
<h4>Description</h4>
<asp:Label ID="DescLabel" runat="server" Text='<%# Eval("Description") %>' />
<br />
</div>
</div>
</ItemTemplate>
</asp:Repeater>
Note the button and the plain jane click event for that button.
So, to fill the repeater, we have this:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not IsPostBack Then
LoadData()
End If
End Sub
Sub LoadData()
Using conn As New SqlConnection(My.Settings.TEST4)
Dim strSQL As String =
"SELECT * FROM Fighters"
Using cmdSQL As New SqlCommand(strSQL, conn)
conn.Open()
Dim rstData As New DataTable
rstData.Load(cmdSQL.ExecuteReader)
Repeater1.DataSource = rstData
Repeater1.DataBind()
End Using
End Using
End Sub
And now we see/get this:
And now that button click from above (the view button).
Protected Sub cmdMyView_Click(sender As Object, e As EventArgs)
Dim btn As Button = sender
Dim rRow As RepeaterItem = btn.NamingContainer
Debug.Print("Row index = " & rRow.ItemIndex)
Debug.Print("DATA ID pk = " & btn.CommandArgument)
Dim hFighter As HtmlGenericControl = rRow.FindControl("hFighter")
Debug.Print("Figher name = " & hFighter.InnerText)
End Sub
output:
Row index = 3
DATA ID pk = 4
Figher name = Lockheed Martin F-35 Lightning II
So, note how the the simple button click picks up the current row of data.
From that, we can use find control, or get the "row index" of the click, or in our case, we also included the database PK id in the button command arugment.
So, VERY hard to make a case to do all those "hand stands" to write code to "inject" a button when darn near ALL of the data aware controls will repeat the data AND the controls for you over and over with great ease, and in fact ZERO code to have such buttons or controls repeat for you.
there are RARE cases to write code to inject, but they should be the last resort, since in 99% of cases, no such code is required, and worse yet, when you post-back, such injected controls will NOT persist, and you have to re-inject on every post back for such pages to work.
Edit: So, this could be used
markup:
<asp:Repeater ID="Repeater1" runat="server">
<ItemTemplate>
<i id="iHotel" runat="server"><%# Eval("HotelName") %></i>
<br />
<asp:CheckBox ID="chkREL" runat="server"
Checked='<%# Eval("Status").ToString() == "Rel" ? true : false %>' />
<br />
<asp:Button ID="Button1" runat="server" Text="Button"
OnClick="Button1_Click" />
<hr />
</ItemTemplate>
</asp:Repeater>
Say code to load:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
LoadData();
}
}
void LoadData()
{
Repeater1.DataSource = General.MyRst("SELECT * FROM tblHotelsA");
Repeater1.DataBind();
}
result is this:
Button click:
protected void Button1_Click(object sender, EventArgs e)
{
Button btn = (Button)sender;
RepeaterItem iRow = (RepeaterItem)btn.NamingContainer;
Debug.Print($"Row click index = {iRow.ItemIndex}");
CheckBox chkRel = (CheckBox)iRow.FindControl("chkREL");
Debug.Print($"Check box checked = {chkRel.Checked}");
HtmlGenericControl iHotel = (HtmlGenericControl)iRow.FindControl("iHotel");
Debug.Print($"Hotel name from 'p' item = {iHotel.InnerText}");
}
output:
Row click index = 1
Check box checked = True
Hotel name from 'p' item = Ramada Lodge
Hi have the following vb code in ASP.NET:
<asp:Repeater ID="Repeater1" runat="server" DataSourceID="SQL_SRC_DEV_HIERACHY">
<ItemTemplate>
<p class="input_title">Hierachy:
<asp:Literal ID="Literal1" runat="server" Text='<%# Eval("Hierarchy_SKey")%>'></asp:Literal><br />
</p>
<asp:DropDownList ID="DropDownList_H" runat="server" DataSourceID="SQL_SRC_DEV_GROUPINGDESCS" DataTextField="Description" DataValueField="FTE_PARENT_SKEY"></asp:DropDownList><br />
</ItemTemplate>
</asp:Repeater>
I now need to get the selectedvalues for each instance of dropdown created, and += to a variable so that I can built a SQL INSERT command based on the selected values.
Can anybody point me in the right direction to achieve this please? Thanks.
You can loop the items in the Repeater in code behind and use FindControl to get the SelectedValue of the DropDownList.
protected void Button1_Click(object sender, EventArgs e)
{
//loop all the items in the repeater
foreach (RepeaterItem item in Repeater1.Items)
{
//use findcontrol to locate the dropdownlist and cast it back to one
DropDownList drp = item.FindControl("DropDownList_H") as DropDownList;
//display the result
Label1.Text += drp.SelectedValue;
}
}
Thanks VDWWD - I have converted to VB and it work perfectly! Much appreciated.
VB version shown below:
Protected Sub GEN_CODE()
Dim txtField As DropDownList
Dim DDL_Values As String = ""
For Each item In Repeater1.Items
//use findcontrol to locate the dropdownlist and cast it back to one
txtField = item.FindControl("DropDownList_H")
//display the result
DDL_Values += " " + txtField.SelectedValue
Next
End Sub
Sort listview using column headings in the LayoutTemplate
I am able to sort a basic list view using asp:SqlDataSource and setting the list view property DataSourceID by pointing it to the asp:SqlDataSource ID. I am having an issue when sorting when not using the asp:SqlDataSource and just DataBinding from the code behind.
SqlDataSource Example:
<asp:ListView ID="ContactsListView" DataSourceID="ContactsDataSource" runat="server">
<LayoutTemplate>
<table width="640px" runat="server">
<tr class="header" align="center" runat="server">
<td>
<asp:LinkButton runat="server" ID="SortByFirstNameButton" CommandName="Sort" Text="First Name" CommandArgument="FirstName" />
</LayoutTemplate>
....
</asp:ListView>
<asp:SqlDataSource ID="ContactsDataSource" runat="server"
ConnectionString="<%$ ConnectionStrings:MainConnString %>"
SelectCommand="SELECT * FROM TableName">
</asp:SqlDataSource>
DataBind Example:
<asp:ListView ID="ContactsListView" DataSourceID="ContactsDataSource" runat="server">
<LayoutTemplate>
<table width="640px" runat="server">
<tr class="header" align="center" runat="server">
<td>
<asp:LinkButton runat="server" ID="SortByFirstNameButton" CommandName="Sort" Text="First Name" CommandArgument="FirstName" />
</LayoutTemplate>
....
</asp:ListView>
protected void Page_Load(object sender, EventArgs e)
{
String SQL = "SELECT * FROM Customer";
SqlDataAdapter da= new SqlDataAdapter(SQL, ConnStr);
DataSet ds = new DataSet();
da.Fill(ds);
ContactsListView.DataSource = ds.Tables[0];
ContactsListView.DataBind();
}
Both code samples populate the list view, but the second example data binding does not work for sorting. With the first example, the sorting just works with the added asp:LinkButton in the LayoutTemplate adding the CommandName="sort" and setting the CommandArugment="ColumnName", but it does not work with the second example.
Can anyone please explain why and how to get the sorting working using the code behind DataBind method?
Thanks!
I solved my issue.
I added an event to handle the sorting. The event grabs the command name (Data column) and passes it and the sorting direction into a function which will make another call to the database sort the returned results and rebind to the List View.
I had to create a view state to hold the List View Sort Direction because for some reason, the onsorting event handler kept saying that the sort direction was ascending.
Front End
<asp:ListView ID="ContactsListView" OnSorting="ContactsListView_Sorting" runat="server">
<LayoutTemplate>
<table width="640px" runat="server">
<tr class="header" align="center" runat="server">
<td>
<asp:LinkButton runat="server" ID="SortByFirstNameButton" CommandName="Sort" Text="First Name" CommandArgument="FirstName" />
</LayoutTemplate>
....
</asp:ListView>
Back End
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
BindContacts(string.Empty);
}
}
protected SortDirection ListViewSortDirection
{
get
{
if (ViewState["sortDirection"] == null)
ViewState["sortDirection"] = SortDirection.Ascending;
return (SortDirection)ViewState["sortDirection"];
}
set { ViewState["sortDirection"] = value; }
}
protected void ContactsListView_Sorting(Object sender, ListViewSortEventArgs e)
{
BindContacts(e.SortExpression + " " + ListViewSortDirection.ToString());
// Check the sort direction to set the image URL accordingly.
string imgUrl;
if (ListViewSortDirection == SortDirection.Ascending)
ListViewSortDirection = SortDirection.Descending;
else
ListViewSortDirection = SortDirection.Ascending;
}
private void BindContacts(string sortExpression)
{
sortExpression = sortExpression.Replace("Ascending", "ASC");
sortExpression = sortExpression.Replace("Descending", "DESC");
using (SqlConnection conn = new SqlConnection(_connStr))
{
conn.Open();
using (SqlDataAdapter dAd = new SqlDataAdapter("SELECT * FROM Customer", conn))
{
DataTable dTable = new DataTable();
dAd.Fill(dTable);
// Sort now
dTable.DefaultView.Sort = sortExpression;
// Bind data now
ContactsListView.DataSource = dTable;
ContactsListView.DataBind();
}
conn.Close();
}
}
I guess you could try to add a handler for ListView's Sorting event. There you are given the sorting column and the sort order in the event arguments. This could be easily usable to build a specific query and bind it to the list.
Because depending on the sort expression (which you defined in your markup) SqlDataSource will very likely do something like this (I'm not sure this is exactly what it does) for you behind the scenes:
Expression<Func<DataRow,object>> myExpression = row => row["SortExpressionYouDefinedForTheColumn"];
IEnumerable<DataRow> ex = ds.Tables[0].AsEnumerable().OrderBy(myExpression.Compile());
Or SqlDataSource may be using a DataView to sort the DataTable.
SqlDataSource can do this because by default it uses a DataSet to store the result set (or so says the documentation):
The data retrieval mode identifies how a SqlDataSource control retrieves data from the underlying database.
When the DataSourceMode property is set to the DataSet value, data is
loaded into a DataSet object and stored in memory on the server. This
enables scenarios where user interface controls, such as GridView,
offer sorting, filtering, and paging capabilities..
Since you chose to bind manually to a DataSet, you need to do the "magic" yourself; in other words, you handle the OnSort command, get the sort expression, get your data source again (however you do it, from Session or by calling the database again) and do your sort similarly to the lines shown above and rebind to your Gridview.
I am trying to update a database table from my datagrid using an event handler and ItemCommand. I manage to call the routine and everything is working fine except the text that is inserted into my database is empty. I managed to track this back to the text not being passed from my datagrids footer to the sql parameters. I tried using a string first and then passing that to the parameters but they were also empty. I am accessing the control using the following line.
sqlcmd.Parameters.Add("#GoodsDesc", SqlDbType.VarChar).Value = CType(e.Item.FindControl("txtGoodsDesc"), TextBox).Text
The control itself is defined using
<asp:TemplateColumn HeaderText="Goods Descriptions">
<ItemTemplate>
<asp:Label runat="server" ID="lblGoodsDesc" Text='<%# Eval("GoodsDesc") %>'></asp:Label>
</ItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtGoodsDesc" runat="server" TextMode="MultiLine" Rows="3"></asp:TextBox>
</FooterTemplate>
</asp:TemplateColumn>
Am I missing something here? It's like the text in the footer isnt being tied to the control before I call it.
HI Ryan, we will need more code then just that. Where are you .Add +ing this parameter in addition where is e.Item.FindControl what event is it?
You need to check if you are on the footer control:
protected void dg_ItemDataBound(object sender, DataGridItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Footer)
{
if (dg.EditItemIndex != -1)
{
((TextBox)e.Item.FindControl("txtGoodsDesc")).Text
}
}
}
Or in vb.net
if (e.Item.ItemType = ListItemType.Footer) then
Dim s as String=String.Empty
s=CType(e.Item.FindControl("txtGoodsDesc"), TextBox).Text
end if
So essentially I discovered that the issue that was occurring was that VB.Net was calling Page_Load before the event itself was being called, and in the Page_Load method I was calling the method that filled the datagrid, which cleared the textboxes in the footer before the values in them were being read.
To stop this I placed a condition around the call to the method in Page_Load
If Not IsPostBack Then
FillDataGrid()
End If
Then I called the FillDataGrid() function as the very last step in the handler, meaning that the data was read in and then the datagrid was bound to the new values.
How do I set the initial value of a databound drop down list in ASP.NET?
For instance, I want the values, but the first value to display should be -- Select One ---, with a null value.
I think what you want to do is this:
<asp:DropDownList ID="DropDownList1" runat="server" AppendDataBoundItems="true">
<asp:ListItem Text="--Select One--" Value="" />
</asp:DropDownList>
Make sure the 'AppendDataBoundItems' is set to true or else you will clear the '--Select One--' list item when you bind your data.
If you have the 'AutoPostBack' property of the drop down list set to true you will have to also set the 'CausesValidation' property to true then use a 'RequiredFieldValidator' to make sure the '--Select One--' option doesn't cause a postback.
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="DropDownList1"></asp:RequiredFieldValidator>
I know this is old, but a combination of these ideas leads to a very elegant solution:
Keep all the default property settings for the DropDownList (AppendDataBoundItems=false, Items empty). Then handle the DataBound event like this:
protected void dropdown_DataBound(object sender, EventArgs e)
{
DropDownList list = sender as DropDownList;
if (list != null)
list.Items.Insert(0, "--Select One--");
}
The icing on the cake is that this one handler can be shared by any number of DropDownList objects, or even put into a general-purpose utility library for all your projects.
What I do is set the text property of the drop down list AFTER I databind it. Something like this:
protected void LoadPersonComboBox()
{
var p = new PeopleBLL();
rcmbboxEditPerson.DataSource = p.GetPeople();
rcmbboxEditPerson.DataBind();
rcmbboxEditPerson.Text = "Please select an existing person to edit...";
}
This makes the initial visible value of this dropdown show up, but not actually be a part of the drop down, nor is it a selectable.
I know this already has a chosen answer - but I wanted to toss in my two cents.
I have a databound dropdown list:
<asp:DropDownList
id="country"
runat="server"
CssClass="selectOne"
DataSourceID="country_code"
DataTextField="Name"
DataValueField="CountryCode_PK"
></asp:DropDownList>
<asp:SqlDataSource
id="country_code"
runat="server"
ConnectionString="<%$ ConnectionStrings:DBConnectionString %>"
SelectCommand="SELECT CountryCode_PK, CountryCode_PK + ' - ' + Name AS N'Name' FROM TBL_Country ORDER BY CountryCode_PK"
></asp:SqlDataSource>
In the codebehind, I have this - (which selects United States by default):
if (this.IsPostBack)
{
//handle posted data
}
else
{
country.SelectedValue = "US";
}
The page initially loads based on the 'US' value rather than trying to worry about a selectedIndex (what if another item is added into the data table - I don't want to have to re-code)
To select a value from the dropdown use the index like this:
if we have the
<asp:DropDownList ID="DropDownList1" runat="server" AppendDataBoundItems="true"></asp:DropDownList>
you would use :
DropDownList1.Items[DropDownList1.SelectedIndex].Value
this would return the value for the selected index.
hi friend in this case you can use the
AppendDataBound="true"
and after this use the list item.
for e.g.:
<asp:DropDownList ID="DropDownList1" runat="server" AppendDataBoundItems="true">
<asp:ListItem Text="--Select One--" Value="" />
</asp:DropDownList>
but the problem in this is after second time select data are append with old data.
Add an item and set its "Selected" property to true, you will probably want to set "appenddatabounditems" property to true also so your initial value isn't deleted when databound.
If you are talking about setting an initial value that is in your databound items then hook into your ondatabound event and set which index you want to selected=true you will want to wrap it in "if not page.isPostBack then ...." though
Protected Sub DepartmentDropDownList_DataBound(ByVal sender As Object, ByVal e As System.EventArgs) Handles DepartmentDropDownList.DataBound
If Not Page.IsPostBack Then
DepartmentDropDownList.SelectedValue = "somevalue"
End If
End Sub
dropdownlist.Items.Insert(0, new Listitem("--Select One--", "0");