Changing FormField ControlMode from code-behind causes strange behaviour

Question

I have created a custom form where I add "Mode" parameter to query string based on the type of form I want to display: New/Display/Edit. Based on the mode from query string I set the ControlMode property of FormFields from code-behind.

I have attached custom forms in a Web-scoped Feature:

public override void FeatureActivated(SPFeatureReceiverProperties properties)
{
    SPWeb web = properties.Feature.Parent as SPWeb;
    web.AllowUnsafeUpdates = true;
    SPList myList = web.Lists.TryGetList("MyList");
    if (myList != null)
    {
        myList.ContentTypes["MyCustomContentType"].EditFormUrl = "_layouts/MyProject/MyForm.aspx?Mode=Edit";
        myList.ContentTypes["MyCustomContentType"].NewFormUrl = "_layouts/MyProject/MyForm.aspx?Mode=New";
        myList.ContentTypes["MyCustomContentType"].DisplayFormUrl = "_layouts/MyProject/MyForm.aspx?Mode=Display";
        myList.ContentTypes["MyCustomContentType"].Update();
    }
    web.AllowUnsafeUpdates = false;
}

Nonetheless there is a need to specify a ControlMode for FormField controls in aspx page, otherwise an error occurs when displaying a page. And that's where the problem begins:

• if I set them to ControlMode="New" in aspx and setting to ControlMode.New from code-behind - New Form is ok

• if I set them to ControlMode="New" in aspx and setting to ControlMode.Display from code-behind - SPContext.Current.ItemId is 0 so the form is not created as Display Form

• if I set them to ControlMode="Display" in aspx and setting to ControlMode.New from code-behind - a folder is created instead of item

• if I set them to ControlMode="Display" in aspx and setting to ControlMode.Display from code-behind - Display Form is ok

I've tried setting the ControlMode property from different event like OnPreInit, OnInit, CreateChildControls, Page_Load without success.

I've even tried to set the properties in aspx literally from code-behind using tricks like ControlMode="<%# _formMode %>" also without success.

The question is: why SharePoint sticks hardly to ControlMode set in aspx page and gets confused when switching it from code-behind? Is creating separate aspx forms for each mode the only solution?

Answer 1

I have chosen the scenario where I set the controls to ControlMode="Display" but I use code-behind workaround in the form's OnInit method to force SharePoint to create an item instead of a folder with this code:

item.FileSystemObjectType = SPFileSystemObjectType.File;

Looks like all my scenarios work fine with this tweak.