I am working on a solution in C# and ASP.NET 4.0 I am trying to get the value of a radiobutton from my page that was dynamically created based on some database information.
Here is what gets generated in the page source:
<td>
<input id="masterMain_3Answer_0" type="radio" name="ctl00$masterMain$3Answer"
value="Y" onclick="return answeredyes(3);" />
<label for="masterMain_3Answer_0">Y</label>
</td>
<td>
<input id="masterMain_3Answer_1" type="radio" name="ctl00$masterMain$3Answer"
value="N" onclick="return answeredno(3,'desc');" />
<label for="masterMain_3Answer_1">N</label>
</td>
Inside the OnClick function of my submit button I want to gather wether Y or N has been selected based on the user's input.
Here is what I have written so far:
RadioButton _rbAnswer = new RadioButton();
RadioButtonList _rbList = new RadioButtonList();
ContentPlaceHolder cp = (ContentPlaceHolder)Master.FindControl("masterMain");
_rbAnswer = (RadioButton)Master.FindControl("masterMain_3Answer_0");
HtmlInputRadioButton rb = (HtmlInputRadioButton)Master.FindControl("masterMain_3Answer_0");
_rbAnswer = (RadioButton)cp.FindControl("masterMain_3Answer_0");
_rbList = (RadioButtonList)cp.FindControl("masterMain_3Answer_0");
I am able to get the ContentPlaceHolder without any issues but the rest of the objects are null after it attempts to get the . I have also attempted removing the "masterMain_" but still doesn't want to find the controls.
Here is the code in which the individual radiobuttonlists are added
TableRow _tempRow = new TableRow();
TableCell _cellOK = new TableCell();
RadioButtonList _rbList = new RadioButtonList();
_rbList.ID = r[0].ToString()+"Answer";
_rbList.RepeatDirection = RepeatDirection.Horizontal;
//add options for yes or no
ListItem _liOk = new ListItem();
_liOk.Value = "Y";
ListItem _linotOk = new ListItem();
_linotOk.Value = "N";
_rbList.Items.Add(_linotOk);
//add cell to row
_rbList.Items.Add(_liOk);
_cellOK.Controls.Add(_rbList);
_tempRow.Cells.Add(_cellOK);
//add the row to the table
stdtable.Rows.Add(_tempRow);
To be able to quickly find dynamically created controls, add a dictionary to your page class:
private Dictionary<string, Control> fDynamicControls = new Dictionary<string, Control>();
then when a new control is created in code and its ID is assigned:
fDynamicControls.Add(newControl.ID, newControl);
and when you need control's reference:
Control c = fDynamicControls["controlIdThatYouKnow"];
When using FindControl don't use the id that's generated by the page. Use the ID that you specified inthe aspx.
If this is inside a Repeateror another DataBound control, you have to first find the current record. (GridViewRow or RepeaterItem) first, an use that item's .FindControl function.
See this (different - not duplicate) question to see a code example of how to do it: How to find control with in repeater on button click event and repeater is placed with in gridview in asp.net C#
When you create dynamic controller give specific ids for them. This facilitate to generate controls with our own id. therefore then we can access the controls with this id.
And also use OnInit life cycle event to generate dynamic controllers, this is the best place to generate them.
RadioButton _rbAnswer = new RadioButton();
_rbAnswer.ID="ranswerid";
Given your update, you'll find that your control heirarchy is fairly deep. You have a RadioButtonList inside a cell inside a row inside a table ...
FindControl is a method that needs to be called on a specific object and can only find objects that are actual children of that object. In this case, you either need to build a recursive method or go directly to the control in question. Since so many of these controls are generated dynamically, you'll have no real way of accessing them directly so building the recursive function may be simplest. However, on very large pages this method can be very resource consuming:
public static WebUserControl FindControlRecursive(this WebUserControl source, string name)
{
if (source.ID.Equals(name, StringComparison.Ordinal))
return source;
if (!source.Controls.Any()) return null;
if (source.Controls.Any(x => x.ID.Equals(name, StringComparison.Ordinal))
return source.FindControl(name);
WebUserControl result = null;
// If it falls through to this point then it
// didn't find it at the current level
foreach(WebUserControl ctrl in source.Controls)
{
result = ctrl.FindControlRecursive(name);
if (result != null)
return result;
}
// If it falls through to this point it didn't find it
return null;
}
This is an extension method that would allow you to call this on your ContentPlaceHolder control:
var _cp = (ContentPlaceHolder)Master.FindControl("masterMain");
RadioButtonList _rbList = _cp.FindControlRecursive("3Answer");
if (_rbList != null)
// ... Found it
Note: Treat the above as psuedo-code. It has not be implemented by me anywhere so may (likely) require tweaking to behave exactly right.
Related
I have been working with Web Forms for a short while now and I have read most of what I have found about this on google. However, I am still unclear on how to work with this properly. I like the picture in this answer, but find it a bit too generic. I have not found one decent, concrete example on how to work with these events.
I am currently creating several controls dynamically in code behind in the Page_Load event:
foreach (Service service in Services)
{
// service div
HtmlGenericControl serviceDiv = new HtmlGenericControl("div");
serviceDiv.ID = service.ID;
serviceDiv.Style.Add(HtmlTextWriterStyle.TextAlign, "center");
outerDiv.Controls.Add(serviceDiv); //outerDiv exists in the aspx page
// service updatepanel
UpdatePanel uPanel = new UpdatePanel()
{
ID = service.ID + "_uPanel",
UpdateMode = UpdatePanelUpdateMode.Conditional
};
serviceDiv.Controls.Add(uPanel);
// status span
HtmlGenericControl statusSpan = new HtmlGenericControl("span");
statusSpan.ID = service.ID + "_statusSpan";
statusSpan.InnerHtml = service.Status;
uPanel.ContentTemplateContainer.Controls.Add(statusSpan);
// show specific content
if (service.Status.Equals(ServiceControllerStatus.Running.ToString()))
{
// status color
statusSpan.Attributes.Add("class", "status-run");
// stop button
HtmlButton stopButton = new HtmlButton();
stopButton.ID = service.ID + "_btnStop";
stopButton.InnerHtml = "<i class=\"fa fa-stop btn-red\"/></i>";
stopButton.Attributes.Add("type", "button");
stopButton.Attributes.Add("runat", "server");
stopButton.Attributes.Add("class", "btn btn-link btn-xs");
stopButton.Attributes.Add("title", "Stop");
stopButton.ServerClick += new EventHandler(BtnStop_Click);
ScriptManager.GetCurrent(this).RegisterAsyncPostBackControl(stopButton);
uPanel.ContentTemplateContainer.Controls.Add(stopButton);
// restart button
HtmlButton restartButton = new HtmlButton();
restartButton.ID = service.ID + "_btnRestart";
restartButton.InnerHtml = "<i class=\"fa fa-refresh btn-blue\"/></i>";
restartButton.Attributes.Add("type", "button");
restartButton.Attributes.Add("runat", "server");
restartButton.Attributes.Add("class", "btn btn-link btn-xs");
restartButton.Attributes.Add("title", "Restart");
restartButton.ServerClick += new EventHandler(BtnRestart_Click);
ScriptManager.GetCurrent(this).RegisterAsyncPostBackControl(restartButton);
uPanel.ContentTemplateContainer.Controls.Add(restartButton);
}
else
{
// status color
statusSpan.Attributes.Add("class", "status-stop");
// start button
HtmlButton startButton = new HtmlButton();
startButton.ID = service.ID + "_btnStart";
startButton.InnerHtml = "<i class=\"fa fa-play btn-green\"/></i>";
startButton.Attributes.Add("type", "button");
startButton.Attributes.Add("runat", "server");
startButton.Attributes.Add("class", "btn btn-link btn-xs");
startButton.Attributes.Add("title", "Start");
startButton.ServerClick += new EventHandler(BtnStart_Click);
ScriptManager.GetCurrent(this).RegisterAsyncPostBackControl(startButton);
uPanel.ContentTemplateContainer.Controls.Add(startButton);
}
// version span
HtmlGenericControl versionSpan = new HtmlGenericControl("span");
versionSpan.ID = service.ID + "_version";
versionSpan.InnerHtml = service.Version;
versionSpan.Attributes.Add("class", "version-text");
serviceDiv.Controls.Add(versionSpan);
What would I gain from creating these in Page_Init? If I create them in Page_Init, how do I access them in Page_Load? Private global lists of UpdatePanels and HtmlButtons feels so unclean.
I know that the ViewState loads between Page_Init and Page_Load, but what does that really mean? Since I don't do full postbacks, but instead use RegisterAsyncPostBackControl to only update the UpdatePanel's on postback, don't I need to re-populate in Page_Load?
If you don't need the ViewState, then you can also create the controls in Page_Load. The ViewState is used to store the values of the controls (which ones depends on the control) and to use them when the PostBack is sent to the server.
For instance, if you have a textbox, the PostBack contains the new value of the textbox and also the old value in the ViewState. The ASP.NET framework now compares those two and raises the TextChanged event if necessary. Without ViewState, this would not be possible.
The best advice you can give regarding dynamically created controls in ASP.NET WebForms is to avoid using them. They increase complexity very fast und are usually not necessary (even if it seems so at first).
In the majority of the cases, there is a much simpler approach, e.g. by using a Repeater. In your case, you have a list of services. You can bind this list to a Repeater and by that avoid to create the controls manually. See this link on how to use a Repeater.
Another upside of using a Repeater is that you can define the UI in the ASPX markup instead of in the code behind file. In your example, you change the UI based upon the status of the service. In this case, using the ItemDataBound-event of the Repeater might be a good option.
I have a class derived from WebControls.TableCell.
When the Text property is set, I call a method that dynamically adds asp:Panels and asp:LiteralControls to the Cell. I want to reference these controls in Javascript, so naturally I tried using the ClientId of the panels in my JS functions. However, these controls have no ClientId set (the string is empty). Why is this? How do I force the ClientIds to be set?
As a temporary solution, I set the ClientIDMode to "static" and created the IDs on my own, but this is not satisfactory because it's hard to reference those IDs in JS. Why? If you assign, for example, "12345" to one control, it gets changed on client side to something like "MainContent_123456". This is bad because the "MainContent" part is not fixed; thus I never know for sure what the real Id on the client side will be. Currently, I can get the control with jQuery using $ctrl = $('[id$='12345']');, but this is dirty because it would get any control that has '123456' in its id.
So, back to the original question: how do I get my ClientIds set automatically for my panels in my custom TableCells?
Edit: Code added
protected void Page_Load(object sender, EventArgs e)
{
this.ClientIDMode = System.Web.UI.ClientIDMode.Static;
}
Code in the method that adds the controls to the custom TableCell:
Panel remainingTextPanel = new Panel();
remainingTextPanel.ID = Guid.NewGuid().ToString();
remainingTextPanel.Style["display"] = "none";
LiteralControl remainingText = new LiteralControl(myText.Substring(initialStringLength, myText.Length - initialStringLength));
remainingTextPanel.Controls.Add(remainingText);
this.Controls.Add(remainingTextPanel);
Panel linkBtnPanel = new Panel();
LinkButton lnkBtn = new LinkButton() {Text = "...", OnClientClick = "toggleDynamicText('" + remainingTextPanel.ID + "'); return false;" };
lnkBtn.Font.Bold = true;
linkBtnPanel.Controls.Add(lnkBtn);
this.Controls.Add(linkBtnPanel);
And the JS Code:
function toggleDynamicText(id) {
$ctrl = $('[id$=' + id + ']');
$(document).ready(function () {
$ctrl.toggle(1000);
});
}
Without seeing any code it's difficult to say what's going on but to access your controls using jQuery you can do the following:
$("#<%=myElement.ClientID%>")
This way it doesn't matter what .NET assigns as the ID.
I've been trying to follow a few tutorials and code examples but something isn't working as I'd expect.
I have a series of textboxes on a webpage and I need to loop through each one and save it's value to the database. The number of textboxes on the page will vary. I load them from a database. They are all added to a table object.
TableCell cellb = new TableCell();
TextBox txtAnswer = new TextBox();
txtAnswer.TextMode = TextBoxMode.MultiLine;
txtAnswer.Rows = 2;
txtAnswer.ID = "field_" + dataRow["fieldID"].ToString();
txtAnswer.Text = "answer"; //this will be got from the database
cellb.Controls.Add(txtAnswer);
so that adds the textbox to the table row. I then have a save button which has the following code
foreach (Control c in Page.Controls)
{
foreach (Control childc in c.Controls)
{
if (childc is TextBox)
{
TextBox tmpText = (TextBox)childc;
tmpField = tmpText.ID.Split('_');
fieldID = Convert.ToInt32(tmpField[1]);
//save value to the database (eventually)
debug.InnerHtml += tmpText.Text; //this just outputs the values for now
}
}
}
So the above should loop though all the page controls and find the textfields as added on the page_load. However, I am now wondering if it's because they don't exist. So when I save the page, it doesn't know of the controls. I can see the table control, but nothing inside it.... any ideas?!
Dynamic controls must be added on each page request. Preferably during the Init event. It sounds like they have not been added yet (again) by the time you iterate through your controls.
Also, if you know your TextBoxes are within a specific control you should probably find that control first and then, using the same approach you are using, iterate over the controls. Two reasons for this are: efficiency and also, on your code, you are only searching two levels down from the page control. This may be ok but it includes other controls that will not contain any of those textboxes.
Why dont you use a Gridview Control and Then Make custom template with Texbox. Then ON Page Load you can add no of Textboxes you want and then loop the gridview and save the data.
First thing. Make sure you are not creating your controls inside an if (!isPostBack){} - as they need recreating on each postback.
Secondly, I don't believe your loop will find all controls as it will only really travel through the first level.
Ideally, you should search for the controls recursivley.
Here is a recursive method that I use - this will help find all controls of a given ID.
/// <summary>
/// Finds a Control recursively. Note finds the first match that exists
/// </summary>
/// <param name="ContainerCtl">Should be the lowest container in the heirarchy, for eg dont choose Master page if you can pick the specific panel</param>
/// <param name="IdToFind">ID of the control you are looking for</param>
/// <returns>the control if found else null</returns>
public static Control FindControlRecursive(Control Root, string Id)
{
if (Root.ID == Id) { return Root; }
foreach (Control Ctl in Root.Controls)
{
Control FoundCtl = FindControlRecursive(Ctl, Id);
if (FoundCtl != null) { return FoundCtl; }
}
return null;
}
Now, what I would do is:
When you create your TextBox's, store all the ID's in an Array. Then when you need to access them, loop through the Array and for each entry, call the above method. this will then return the TextBox you need.
I have defined a placeholder in my page like this;
<asp:PlaceHolder ID="attrPlaceHolder" runat="server"></asp:PlaceHolder>
I am populating this place holder from a database table using query string productId like this;
// obtain the attributes of the product
DataTable attrTable = CatalogAccess.GetProductAttributes(productId);
// temp variables
string prevAttributeName = "";
string attributeName, attributeValue, attributeValueId;
// current DropDown for attribute values
Label attributeNameLabel;
DropDownList attributeValuesDropDown = new DropDownList();
// read the list of attributes
foreach (DataRow r in attrTable.Rows)
{
// get attribute data
attributeName = r["AttributeName"].ToString();
attributeValue = r["AttributeValue"].ToString();
attributeValueId = r["AttributeValueID"].ToString();
// if starting a new attribute (e.g. Color, Size)
if (attributeName != prevAttributeName)
{
prevAttributeName = attributeName;
attributeNameLabel = new Label();
attributeNameLabel.Text = "<li class=\"txt\">" + attributeName + ":</li>";
attributeValuesDropDown = new DropDownList();
attrPlaceHolder.Controls.Add(attributeNameLabel);
attrPlaceHolder.Controls.Add(attributeValuesDropDown);
}
// add a new attribute value to the DropDownList
attributeValuesDropDown.Items.Add(new ListItem(attributeValue, attributeValueId));
}
However, when inside a button click event, when I loop through this place using visual studio debugging, I saw that the visual studio studio debugger first hit the "attrPlaceHolder.Controls" word in my foreach loop, then secondly comes to 'in' keyword (in foreach loop) but it isn't hitting the first two words (i-e 'Control cnt' in my foreach loop. Here it looks;
protected void ButtonBuyNow_Click(object sender, EventArgs e)
{
// Retrieve the selected product options
string options = "";
foreach (Control cnt in attrPlaceHolder.Controls)
{
if (cnt is Label)
{
Label attrLabel = (Label)cnt;
options += attrLabel.Text;
}
if (cnt is DropDownList)
{
DropDownList attrDropDown = (DropDownList)cnt;
options += attrDropDown.Items[attrDropDown.SelectedIndex] + "; ";
}
}
// Add the product to the shopping cart
ShoppingCartAccess.AddItem(productId, options);
}
Basically I need 'options' variable to be populated but it isn't hitting the foreach loop inside, therefore I am not able to get the 'options' variable populated.
This is a serious problem in my application. Please tell me why I can't get the inside the foreach loop.
NOTE:
please note that this isn't the complete code of my entire page. My rest of the code executes correctly.
why I can't get the inside the foreach loop
Because the list is empty.
Why is the list empty? (Would be the next logical question)
Because, at ASP.Net, dynamically created controls must be re-created at Page_Init in order to exist. When you create them at this stage, the page lifecycle will bind the viewstate and will be ready for use.
If you receive a postback (from the button, for example) and don't recreate them, they simply don't exist.
I created a few radiobuttonlist controls on my project, they're created every time the page is loaded, i want to get the value of the radiobutton that the user has selected, but since my radiobuttons were created dynamically, i don't know how to acces to their values nor how to create their event handlers. Is there a way to assign a name or id to the control when i create it?
i hope you can help me.
I create a seires of radiobuttlist on the page_load event, with the text and their values been pulled out of a database. now, the user has to choose one of the options from that radiobuttlist and i want to get the value of the radiobutton the user checked. how do i do that if i don't know the name nor the id of the radiobuttlist since they're created dynamically.
this is what i've got:
for (int i = 3; i < numfields; i++) {
if (dr[i].ToString() != "" && dr[i] != null){
r.Items.Add(new ListItem(dr[i].ToString(), dr[i].ToString()));
//r.SelectedIndexChanged += new EventHandler(rowSelectedIndex);
}
}
so basically i use my datareader to loop through the data in the database, if the value from the field isn't empty or null, then i add an item to the radiobuttlist called "r"
i tried to create an eventhandler for that too, but since i have never worked with them i really don't know what to do. :(
I'm so sorry if i seem way too pathetic.
Taking a quick look at your code:
for (int i = 3; i < numfields; i++) {
if (dr[i].ToString() != "" && dr[i] != null){
r.Items.Add(new ListItem(dr[i].ToString(), dr[i].ToString()));
//r.SelectedIndexChanged += new EventHandler(rowSelectedIndex);
}
}
The most obvious thing that jumps out is your if statement. You should first check for null:
if (dr[i] != null && dr[i].ToString() != ""){
As if dr[i] is null, you'll get an exception (as you'll be trying to call the ToString() method on a null object.
If the contents of dr are always going to be strings, you might consider writing:
if(!String.IsNullOrEmpty(dr[i]){
I also note you start your indexing at 3 - is this because you want to skip the first 3 fields?
Wherever you create your variable, 'r', you can set the name and ID properties. You can use the ID property to look for the control on PostBack. So if you created your radiolist like so:
RadioButtonList r = new RadioButtonList();
r.Id = "MyRadioButtonList";
r.SelectedIndexChanged += MyRadioButton_SelectedIndexChanged;
Which would point at the following event handler:
private void MyRadioButton_SelectedIndexChanged(Object sender, EventArgs e) {
... Do Stuff ...
}
There are several ways of finding your control when you post back; you can look in the Request.Forms collection for a control matching the name of the control you submitted, or, more appropriately, you can use the FindControl method with the ID you gave the control. See C#, FindControl for a post with a method (by Jeff Atwood!) that will search the entire hierarchy of controls for your control.
When you add a dynamic control is important, too. If you add it too late in the page lifecycle then it will not be available on PostBack. See http://support.microsoft.com/kb/317515 for more details on just when to add a control. There are plenty of resources for Dynamic ASP.Net controls around too.
You could put your RadioButton into a list as you create them. This is also when you want to add your handlers.
RadioButton rb;
for (int i = 1; i < 5; i++)
{
rb = new RadioButton();
rb.AutoSize = true;
rb.Location = new System.Drawing.Point(25, (i*25) + 25);
rb.Name = "radioButton" + i.ToString();
rb.Text = "radioButton" + i.ToString();
//Add some event handler?
this.Controls.Add(rb);
lstRadioButton.Add(rb);
}
Whenever you want to know which one is selected you can do a foreach loop of your list and look if your RadioButton is checked.
foreach (RadioButton rButton in lstRadioButton)
{
if (rButton.Checked == true)
{
//Do something
}
}
You are maybe searching for TagName property if the programmatic name isn't enough for you.
The problem is that you are creating the controls in page_load. In order for their values to be posted back into the controls correctly, you must move this creation into the page_init method and recreate them every time.
Then, in page_load, you can access the values in the controls correctly. If you give them IDs using a consistent naming convention, you will be able to find them using the FindControl method or, in page_init, you can store them in a collection at the page or user control level.