CODEWITHSUNDEEP
c#winformsbindingwindows-forms-designer
Peter Stjernholm Meldgaard
Peter Stjernholm Meldgaard

Reputation: 250

Binding error in design and runtime on usercontrol

In great need help with the strange binding problem with regards to Winform UserControls.

Its like this.

No problem in designer of the UserControl itself.

But entering the designer og the Form containing the UserControl, I get a designer error window with the message: "Cannot bind to the property or column CreateDate on the DataSource. Parameter name: dataMember"

In runtime I get the same error, but first when Show is called on the form. Here I can see on the stack trace that it is thrown after a CheckBinding call.

The error occurs no matter if the DataSource on the bindingSource is set or not during the creation (in constructor) or Load event on the form.

I can see that the designer sets my data source like this in the designer file: this.bindingSourceRecipe.DataSource = typeof(Data.Entities.Recipe);

I have tried so many things to solve this problem. It seems very strange as this is a dead simple form/control setup and should be a trivial use of Winforms usercontrols.

If I set the bindingSourceRecipe.DataSource at runtime to a temp. instance just after the InitializeComponent() in the form then no error occure;

InitializeComponent();
ucRecipeBaseControl.Recipe = new Recipe() { Id = 0, CreateDate = DateTime.Now, Name = "" };

So it seems that the Initialization cycle of the form/control somehow clears the binding source knowledge about its DataSource type.

This does of course not happen if a place all the user controls and BindingSource Directly on the form. Then everythings works, and it does not matter if the DataSource ever gets set to an instance of a Data entity.

Seems like a complete mystery to me, should be dead simple, and I'm kind of lost on what to do.

Any help or suggestions are highly appreciated.

BR Peter Meldgaard

Upvotes: 2

Views: 1009

Answers (1)

Peter Stjernholm Meldgaard
Peter Stjernholm Meldgaard

Reputation: 250

Ahhh, got it nailed at last. It was caused by a mix of Winform designer behavior and my code. I was setting the binding controls datasource in a public property setter, so I could save a copy of the entity, to be able to compare the changed and the org. The thing is that when you put a control with a public property on a form, then the designer initializes this property to null inside the designer generated code. I did not know that. So everytime the usercontrol was instantiated, the DataSource got set to null, clearing the typeof(dataentity), albeit loosing the binding information.

Adding a null check in the setter, and only update datasource when value is not null fixed the issue.

Upvotes: 2

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