I have a datagrid (Asp.Net) with dynamically generated checkbox column..I am not able to generate the checkedChanged event for the checkbox..
Here is my code:
public class ItemTemplate : ITemplate
{
//Instantiates the checkbox
void ITemplate.InstantiateIn(Control container)
{
CheckBox box = new CheckBox();
box.CheckedChanged += new EventHandler(this.OnCheckChanged);
box.AutoPostBack = true;
box.EnableViewState = true;
box.Text = text;
box.ID = id;
container.Controls.Add(box);
}
public event EventHandler CheckedChanged;
private void OnCheckChanged(object sender, EventArgs e)
{
if (CheckedChanged != null)
{
CheckedChanged(sender, e);
}
}
}
and Here is the event
private void OnCheckChanged(object sender, EventArgs e)
{
}
Thanks In advance
When do you add your custom column? If it is on load, then it is too late. Load it on init. I.e. following works with your code:
protected void Page_Init(object sender, EventArgs e)
{
ItemTemplate myTemplate = new ItemTemplate();
myTemplate.CheckedChanged += new EventHandler(myTemplate_CheckedChanged);
TemplateField col = new TemplateField();
col.ItemTemplate = myTemplate;
col.ItemStyle.Wrap = false;
grid.Columns.Add(col);
}
If your checkbox ID's are not being set the same way on every postback, then they can never be connected to the event handlers when it comes time to process the events. Where is your field "id" coming from?
Related
I have my website running on dotnetnuke 7.4, i have a checklistbox which i bind on the page load, and after selecting items from it, user clicks on the submit button, the selected items should save in database, however when i click on the submit button, checklistbox gets blank, i tried to enable ViewState at :
Web.config level
Page Level
Control Level
But all in vain, it still unbinds checklistbox because of which everything disappears, i tried the same in plain .net and it works like a charm.
Is there any specific settings in dotnetnuke to support viewstate, or is there any other better option to achieve this.
Here's my code:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Entities objEntities = new Entities();
List<Entities> obj = objEntities.GetList(2);
chkBox.DataSource = obj;
chkBox.DataTextField = "Name";
chkBox.DataValueField = "ID";
chkBox.DataBind();
}
}
protected void btnSubmit_Click(object sender, EventArgs e)
{
foreach (ListItem item in chkBox.Items)
Response.Write(item.Text + "<br />");
}
There's the issue. Remove that (!IsPostBack) check in your page_load event. Have your code to be like below. Else, only at first page load you are binding the datasource to control which gets lost in postback.
protected void Page_Load(object sender, EventArgs e)
{
Entities objEntities = new Entities();
List<Entities> obj = objEntities.GetList(2);
chkBox.DataSource = obj;
chkBox.DataTextField = "Name";
chkBox.DataValueField = "ID";
chkBox.DataBind();
}
OR, to be more efficient; refactor your code to a method like below and store the data object in Session variable like
private void GetDataSource()
{
List<Entities> obj = null;
if(Session["data"] != null)
{
obj = Session["data"] as List<Entities>;
}
else
{
Entities objEntities = new Entities();
obj = objEntities.GetList(2);
}
chkBox.DataSource = obj;
chkBox.DataTextField = "Name";
chkBox.DataValueField = "ID";
chkBox.DataBind();
Session["data"] = obj;
}
Call the method in your Page_Load event like
protected void Page_Load(object sender, EventArgs e)
{
GetDataSource();
}
I implemten ITemplate to dynamically create a Template field
TemplateField isReqField = new TemplateField();
isReqField.HeaderText = "Lizenz anfordern";
isReqField.ItemTemplate = new GridViewTemplate(DataControlRowType.DataRow, DataControlRowState.Normal, "isRequested", "bool");
isReqField.EditItemTemplate = new GridViewTemplate(DataControlRowType.DataRow, DataControlRowState.Edit, "isRequested", "bool");
gvLicence.Columns.Add(isReqField);
I implement InstantiateIn
public void InstantiateIn(System.Web.UI.Control container)
{
...
CheckBox ckRequest = new CheckBox();
ckRequest.ID = "ckRequest";
ckRequest.DataBinding += new EventHandler(this.CkIsRequested_DataBinding);
container.Controls.Add(ckRequest);
...
}
with the DataBinding Handler
private void CkIsRequested_DataBinding(Object sender, EventArgs e)
{
CheckBox ckRequest = (CheckBox)sender;
GridViewRow row = (GridViewRow)ckRequest.NamingContainer;
ckRequest.Checked = (bool)DataBinder.Eval(row.DataItem, columnName);
}
But then in the RowUpdating Handler I cannot find my checkBox Control with the FindControl Method:
protected void gvLicence_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
CheckBox chb = (CheckBox)gvLicence.Rows[e.RowIndex].FindControl("ckRequest");
bool requestValue = chb.Checked;
It throws an Exeption because gvLicence.Rows[e.RowIndex].FindControl("ckRequest") is null.
Many thanks for your attention and help.
So I have a listbox on my page and some textfields. Through the textfields I can add an item to my listbox (click the button, it adds it to a private List<string> which is then set as a ViewState and the list is databound again).
My listbox is also in an updatepanel which gets triggered on the button's Click event.
Problem: My Viewstate remains null on a postback so it gets reset each time.
Some code:
private List<IngredientData> _ingredientsList;
protected void Page_Load(object sender, EventArgs e)
{
// prepare ingredient lists
_ingredientsList = new List<IngredientData>();
if (Page.IsPostBack)
{
if (ViewState["IngredientsList"] != null)
{
_ingredientsList = (List<IngredientData>) ViewState["IngredientsList"];
}
}
lstIngredients.DataSource = _ingredientsList;
lstIngredients.DataTextField = "Text";
lstIngredients.DataValueField = "Name";
lstIngredients.DataBind();
}
protected void btnAddIngredient_Click(object sender, EventArgs e)
{
_ingredientsList.Add(new IngredientData { Name = txtIngredientName.Text, Quantity = txtUnitQuantity.Text, Unit = lstUnits.SelectedValue });
ViewState["IngredienstList"] = _ingredientsList;
lstIngredients.DataSource = _ingredientsList;
lstIngredients.DataBind();
}
Any idea how I can fix this? Am I doing something wrong?
btnAddIngredient_Click is adding to "IngredienstList" not "IngredientsList" (note the spelling).
You can avoid this kind of typo by using a constant:
private const string IngredientsListViewStateKey = "IngredientsList";
then referring to it like this:
ViewState[IngredientsListViewStateKey] = _ingredientsList;
I Add Control Dynamiclly but; easc Postback event my controls are gone. I Can not see again my controls.
So How can I add control ?
Because you must recreate your controls on every postback,
see this article
Add the controls in the Page's Init event and they will be preserved in viewstate when posting back. Make sure they have a unique ID.
See this link...
ASP.NET Add Control on postback
A very trivial example..
public partial class MyPage : Page
{
TextBox tb;
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
tb = new TextBox();
tb.ID = "testtb";
Page.Form.Controls.Add(tb);
}
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
//tb.Text will have whatever text the user entered upon postback
}
}
You should always assign a unique ID to the UserControl in its ID property after control is loaded. And you should always recreate UserControl on postback.
To preserve posback data (i.e. TextBox'es) you must load UserControl in overriden LoadViewState method after calling base.LoadViewState - before postback data are handled.
Add controls in runtime and save on postback:
int NumberOfControls = 0;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ViewState["b1"] = 0;
}
else
{
if ((int)ViewState["b1"] > 0)
{
CreateBtn();
}
}
}
protected void btn1_Click(object sender, EventArgs e)
{
NumberOfControls = (int)ViewState["b1"];
Button b1 = new Button();
// b1.Attributes.Add("onclick", "x()");
b1.Text = "test2";
b1.ID = "b1_" + ++NumberOfControls;
b1.Click +=new System.EventHandler(btn11);
Panel1.Controls.Add(b1);
ViewState["b1"] = NumberOfControls;
}
protected void CreateBtn()
{
for (int i = 0; i < (int)ViewState["b1"];i++)
{
Button b1 = new Button();
// b1.Attributes.Add("onclick", "x()");
b1.Text = "test2";
b1.ID = "b1_" + i;
b1.Click += new System.EventHandler(btn11);
Panel1.Controls.Add(b1);
}
}
protected void btn11(object sender, System.EventArgs e)
{
Response.Redirect("AboutUs.aspx");
}
i careate button control and place in panel but not working?
protected void Button1_Click(object sender, EventArgs e)
{
Button btn = new Button();
btn.Text = "Test button";
Panel1.Controls.Add(btn);
btn.Click += new EventHandler(btn_Click);
}
void btn_Click(object sender, EventArgs e)
{
Response.Write("<script>alert('test')</script>");
}
When you dynamically add controls to your page, you have to re-add them on any subsequent request (postback). The button you added in Button1_OnClick will not automatically be recreated in a subsequent request (e.g. in a postback).
There a lot's of similar questions about this topic, where you can find details. For examples, use the following search:
https://stackoverflow.com/search?q=dynamic+control+event+[asp.net]
Make sure you assign an ID to the button, and make sure it's the same everytime you create it.
Create the control in the CreateChildControls overload, adding it once in response to another event isn't going to be enough to keep it on the page.
You're best bet is going to be tracking the whether the button needs to be created or not:
bool CreateButton
{
get
{
if (ViewState["CreateButton"] == null)
return false;
return (bool)ViewState["CreateButton"];
}
set
{
ViewState["CreateButton"] = value;
}
}
override void public CreateChildControls ()
{
panel1.Controls.Clear ();
if (CreateButton)
{
Button btn = new Button();
btn.Text = "Test button";
btn.ID = "CreatedButton"; // Note the ID here...
Panel1.Controls.Add(btn);
btn.Click += new EventHandler(btn_Click);
}
}
protected void Button1_Click(object sender, EventArgs e)
{
CreateButton = true;
EnsureChildControls ();
}
void btn_Click(object sender, EventArgs e)
{
Response.Write("<script>alert('test')</script>");
}
Something like that should work for you...