Develop Reference

Unable To Render Control To Placeholder

The following code will not add a control to an aspx placeholder:
var control = new ASCXControl { ID="searchFilters", Filters = filters };
var placeholder = Utility.FindControlRecursive(Page, "rightColumnSearchFilters") as PlaceHolder;
if(placeholder != null){
placeholder.Controls.Add(control);
placeholder.Visible = true;
}
When debugging, the placeholder is found and the control shows as added to the placeholder controls collection after entering the block, but yet I see nothing render into the placeholder on the page.
I currently need to pass variables to the control in order to find the filters I need to display. Although I don't like passing variables between controls, I don't see any other way.
What am I missing would make the control not render? Is there a better way to do this?
EDIT:
I am trying to get the HTML inside of the ascx to render. I am able to get the Filters parameters inside the Page_Load on the control.

This may or may not be the whole problem, but usually trying to instantiate a UserControl the way you're doing it leads to problems. You should do it using the LoadControl(path) method of the Page class:
ASCXControl ctl = (ASCXControl) LoadControl("path");
I'm not 100% sure, but I think that if you just instantiate it like an ordinary class/control, you wind up not running all the event handlers (such as Load) that you usually would.

dynamically adding validators

In my case I would like to dynamically add validators to my control based on given logic. For each control I first check something in my DB and if it goes aout that field is required I would like to add requiredField to that control. I firt iterate through each control and if its required I add attribute required="true".
I added this code but it doens work I mean nothing happens, none validation is being made.
if(gc.Attributes["controlid"] != null)
{
RequiredFieldValidator validator = new RequiredFieldValidator();
validator.ControlToValidate = gc.Attributes["controlid"];
validator.ErrorMessage = gc.Attributes["errormessage"];
this.Controls.Add(validator);
}
Thanks for any suggestions.

You also have to add it to the Page's validators collection in order for the server side validation to occur. Adding it just to the page controls collection as you did is what is needed to get the JavaScript validation to get rendered to the browser.
Page.Validators.Add(validator);

Are you adding your Validator control to the same container as the control it validates? Validator controls require the target control to be in the same INamingContainer.

How to get a list of controls on a asp page and set an attribute dynamically?

So I was told the following would not be possible:
I have a aspx page that has a number of dropdowns. Each dropdown is set with either a class=leftcolumn or class=rightcolumn.
I need to assign an attribute:
propertyID.Attributes["nameOfAttribute"] = "false";
But instead of manually writing out each controlID and setting its attribute with the line above, I had hoped there was a way to go through and set the attribute on each control ID if it had class=leftcolumn.
This is something I know is possible to do through JQuery easily, but I need it on the code behind during load.
Thanks,

I'm not familiar enough with JQuery to write a sample of it, but you could always register a startup script in your code behind to execute when the page loads.
string myJQueryString = ; //some jquery script to set your variables
this.ClientScript.RegisterStartupScript(typeof(MyPage), "key", myJQueryString);

As Steve said you can do it easily with JQuery javascript library
first your should add a refrence of this library to you aspx pages then
$("select[class=leftcolumn]").each(function(index, value) {
// You are selecting all of the dropdowns with the class attribute equal to (leftcolumn)
$(value).attr("yourCustomAttribute") = someValue;
});

I guess I didn't specify clearly in my question so I am answering my own so I can ask again in a completely new thread - but I want to do this in C# in the code behind, not using JQuery.

ASP.NET: aggregating validators in a user control

I am developing a web application where I would like to perform a set of validations on a certain field (an account name in the specific case).
I need to check that the value is not empty, matches a certain pattern and is not already used.
I tried to create a UserControl that aggregates a RequiredFieldValidator, a RegexValidator and a CustomValidator, then I created a ControlToValidate property like this:
public partial class AccountNameValidator : System.Web.UI.UserControl {
public string ControlToValidate {
get { return ViewState["ControlToValidate"] as string; }
set {
ViewState["ControlToValidate"] = value;
AccountNameRequiredFieldValidator.ControlToValidate = value;
AccountNameRegexValidator.ControlToValidate = value;
AccountNameUniqueValidator.ControlToValidate = value;
}
}
}
However, if I insert the control on a page and set ControlToValidate to some control ID, when the page loads I get an error that says Unable to find control id 'AccountName' referenced by the 'ControlToValidate' property of 'AccountNameRequiredFieldValidator', which makes me think that the controls inside my UserControl cannot resolve correctly the controls in the parent page.
So, I have two questions:
1) Is it possible to have validator controls inside a UserControl validate a control in the parent page?
2) Is it correct and good practice to "aggregate" multiple validator controls in a UserControl? If not, what is the standard way to proceed?

Addressing your second question first- I don't think it's a good idea to "aggregate" validators together this way unless you include the controls you're validating in the user control. Too much work for not enough payoff.
You could fix this problem by exposing properties on your AggregatedValidator to set the names of the controls to validate, and pass in the ClientID of those controls you want validated.

I believe ASP.NET expects the ControlToValidate ID to be in the same naming container. You can probably override the validation method and use Parent.FindControl.
EDIT: This might be a good place to use a CompositeControl rather than a UserControl. They are designed for just this kind of aggregation. But you might have a similar NamingContainer issue.

ASP.net validation from codebehind

I created an entry template for data which is repeated several times. Now I want to make sure at least one of these items is filled in.
the way I do this is use the Count property from a generic list List to see how many are are used(there's some logic in my control that allows me to just pick out the entries that are actually used).
Is there any way I can add something to the validationsummary of the page to notify the user that at least one itme needs to be filled in.
I want to do the count-check in the code behind ...
if (EnteredClasses.Count > 0)
{
//do stuff here
}
else
{
//show validation error
}

I would use the CustomValidator control, inline with the ServerValidate function and also check for the Page.IsValid. The error message then for your CustomValidator control will show up in the validation summary if the ServerValidate function sets the args.IsValid to false.
Andrew

Use a CustomValidator. When using these you can write any logic you like.

I would cheat and merge two methods. As per your question you seem to require the use of the validation summary so you need the basic asp validation. Then you need to use a custom validator.
The problem with the custom validator, is that you must attach it to a particular control and then implement the javascrip method
function ClientValidate(source, agruments)
{
// Do your check here where source is the span for the validator and
// argument is an object with .value the value of the control to which
// the validator is attached and .isvalid that indicate if the validation
// checks out (that's what you set to true or false)
}
The problem if that you want to validate multiple items not juste one. so I would implement this method and ignore arguments.value to then use jQuery to check your whole form and do whatever validation you need and then set isvalid.