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PObind DateTimePicker to a DB column of datatype time(0)
 

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  1. PObind DateTimePicker to a DB column of datatype time(0)
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    <p>I have a SQL Server table and I'm trying to bind controls to the corresponding columns of this table (I'm using EF4). One of the columns is of datatype <code>time(0)</code> which is bound to a <code>DateTimePicker</code> control. </p> <p>The picker has a custom format of <code>HH:mm</code>. It also should treat <code>NULL</code> values in the DB table, therefore I added to it custom <code>Format</code> and <code>Parse</code> event handlers. The DB column is bound to the picker's <code>Text</code> property, and the picker shows correctly the time values in the DB table, including <code>NULL</code> values. (I tried the <code>Value</code> property, but the picker didn't show DB values correctly).</p> <p>The problem is that when I do <code>context.SaveChanges()</code>, all the values are saved to the DB except for the picker value. I don't get any error message or something similar, so I can't understand why the picker fails to save its value. Changing only the picker value doesn't seem to have any effect on the DB table.</p> <p>Any help or suggestion will be appreciated.</p> <p>Here is my code:</p> <pre><code>Private Sub MyScreen_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load Dim b As Binding = MyTimePicker.DataBindings.Item("Value") AddHandler b.Format, New ConvertEventHandler(AddressOf dtp_Format) AddHandler b.Parse, New ConvertEventHandler(AddressOf dtp_Parse) context = New MyDBEntities() Me.ProductsBindingSource.DataSource = context.Products End Sub Private Sub dtp_Format(sender As Object, e As ConvertEventArgs) Dim bnd As Binding = CType(sender, Binding) If bnd IsNot Nothing Then Dim dtp As DateTimePicker = CType(bnd.Control, DateTimePicker) If dtp IsNot Nothing Then If e.Value Is Nothing Then dtp.Checked = False e.Value = dtp.Value Else dtp.Checked = True dtp.Value = dtp.Value.Date + e.Value End If End If End If End Sub Private Sub dtp_Parse(sender As Object, e As ConvertEventArgs) Dim bnd As Binding = CType(sender, Binding) If bnd IsNot Nothing Then Dim dtp As DateTimePicker = CType(bnd.Control, DateTimePicker) If dtp IsNot Nothing Then If Not dtp.Checked Then dtp.ShowCheckBox = True dtp.Checked = False e.Value = DBNull.Value Else Dim val As DateTime = Convert.ToDateTime(e.Value) e.Value = New Nullable(Of DateTime)(val) End If End If End If End Sub </code></pre> <p><strong>UPDATE</strong></p> <p>OK, I changed the picker databinding to bind to the <code>Value</code> property instead of <code>Text</code>, and changed the <code>dtp_Format</code> code so that the picker shows the correct value.</p> <p>There seems to be a problem with the picker validation, which probably prevents saving the picker value to the DB. If I change the picker value and try to move to another field, the <code>Validating</code> event is fired but not the <code>Validated</code> event, the focus doesn't move to the next field and I can't close the form. If I put <code>DateTime.TryParse(MyTimePicker.Value, tmp)</code> inside the <code>Validating</code> event and it returns <code>True</code>. If I set <code>CausesValidation = False</code> the problem is gone but still the picker value isn't saved to the DB.</p> <p>I also noticed during debugging that <code>e.Value</code> inside <code>dtp_Format</code> method is of type <code>TimeSpan</code> whereas <code>e.Value</code> inside <code>dtp_Parse</code> is of type <code>DateTime</code>. Maybe it's what causes the problem? I tried to use <code>TimeSpan</code> inside of <code>DateTime</code> in the code of <code>dtp_Parse</code> but to no avail. </p>
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    1. COIt seems like binding to the Text property might be the reason for this problem. The selections are stored in `.Value` and thus this is the property which should be "binded". The reason why you got an error is, most likely, because this is a date variable and the corresponding column in the DB is text; you should either adapt your database or bind `.Value` such that it is treated as a string. After a quick research, I found quite a few references to this second option (although most of them for WPF). I cannot be of further help (have never been in such a situation).
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    2. COHow do I "bind `.Value` such that it is treated as a string"? I don't seem to find the way to do it in the code or the edmx designer. Could you give me the references you found, please?
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    3. COThese ones are in Winforms (for a MaskedTextBox): http://stackoverflow.com/questions/2329164/how-to-apply-formatting-string-when-binding-datetime-to-maskedtextbox http://stackoverflow.com/questions/982261/bind-nullable-datetime-to-maskedtextbox/986666#986666 and here quite a few in google: https://www.google.com/search?q=binding+date+as+string+vb.net&oq=binding+date+as+string+vb.net&aqs=chrome..69i57.6899j0j7&sourceid=chrome&espv=210&es_sm=93&ie=UTF-8
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