Check TextBox Bindingsource Field Data Type

[wes4dbt]

Lets say I have a form with several Textboxes that are all bound to "bindingsource1". I'd like to be able to check the field data type each textbox is bound to. Something like this,

        Dim ctl As Control
        For Each ctl In frm.Controls
            If ctl.GetType.IsAssignableFrom(GetType(TextBox)) Then
                if ctl 'data type of field' = "Text" then
                    'then check if text is entered
                end if
                if ctl 'data type of field' = "Number" then
                    'then check if a number is entered
                end if 
            End If
        Next

I've been searching but can't find anything on this subject. Maybe I'm not wording my search right.

Any information or suggestion would be appriciated.

[wes4dbt]

Is this possible?

[wes4dbt]

Thought I'd ask one last time.

[jmcilhinney]

When you bind a control property in WinForms you are creating an instance of the Binding class. You'd use it to get that information, e.g.

Dim b As Binding = Me.TextBox1.DataBindings("Text")
 
If b Is Nothing Then
    MessageBox.Show("Property not bound")
Else
    Dim dataSource As Object = b.DataSource
    Dim propertyName As String = b.BindingMemberInfo.BindingField
    Dim prop As PropertyInfo = dataSource.GetType().GetProperty(propertyName)
    Dim dataType As Type = prop.PropertyType
 
    MessageBox.Show(dataType.ToString())
End If

[jmcilhinney]

Actually, that's not going to work in all cases. I'll investigate a bit further.

[wes4dbt]

jmc,

Thanks for the reply.

I tried your code but had some problems. This line,

Dim prop As PropertyInfo = dataSource.GetType().GetProperty(propertyName)

Gave me an errror "Type 'PropertyInfo' not defined "

So I worked around that problem by writing the code like this,

        Dim b As Binding = Me.SCRNSTextBox.DataBindings("Text")
        If b Is Nothing Then
            MessageBox.Show("Property not bound")

        Else
            Dim dataSource As Object = b.DataSource
            Dim propertyName As String = b.BindingMemberInfo.BindingField
            'Dim prop As PropertyInfo = dataSource.GetType().GetProperty(propertyName)
            Dim dataType As Type = dataSource.GetType().GetProperty(propertyName).PropertyType
        End If

But this line,

Dim dataType As Type = dataSource.GetType().GetProperty(propertyName).PropertyType

Gave me an error "Object reference not set to an instance of an object"
I tried several variation but with no luck.

BTW - Debug.Print( datasource.gettype.tostring ) prints "system.windows.Forms.BindingSource"

[jmcilhinney]

This sort of thing shouldn't really need to be explained to someone with close to a thousand posts but here goes. If you want to use a type name unqualified in code then you must import the namespace that that type is a member of. If you don't know what namespace that is, simply read the documentation for the type.

As for the NullReferenceException, I did mention that that code wouldn't work. It only works if you bind directly to an object with a property with that name, which you're not in the case of a BindingSource. It would require you to use PropertyDescriptors but, at this stage, I'm not exactly sure how.

[wes4dbt]

jmc,

In my defence, 90% of those post where in the Reporting or VB6 forum. Anyway I should have thought it through but now I've fixed the first isssue.

At sometime in the future you have any new information on the NullReferenceException issue Id be glad to hear about. For now, I'll move on with plan B.

Thanks for the reply