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Visual Studio 2008 Multiselection querry with LINQ Query

With Visual Studio 2008 and SQL Server 2005 I have a Form where i drag the data Class (tbl_Name ) Linked to a Table Named tbl_Name

The Table has 5 Column : NameID/Name/Town/Country/Continent

So the Form show a Grid representing the tbl_Name with the 5 column
I have in same form Toolstrip 2 combo box named as follow :

ToolStripComboBox1 It Populate Taking Data from the column Continent
ToolStripComboBox2 It Populate Taking Data from the collumn Country

In the Form I have also a Button : Button3 that i use to trigger the filter action

I am using the following code to filter the Grid by Continent and by Country and it works very well

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click

Dim MultyQuerry = From tbl_Name In db.tbl_Names _
Where tbl_Name.Continent = Me.ToolStripComboBox1.SelectedItem.ToString _
And tbl_Name.Country = Me.ToolStripComboBox2.SelectedItem.ToString _
Select tbl_Name
Me.Tbl_NameBindingSource.DataSource = MultyQuerry
End Sub

Now let me come to my Problem

All is working if i have both Combo Box with a value :

But it give me error if one of the comboBox is empty

Is anyone helping me to change my code so to handle the Null value ???

Thanks

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Nasir Razzaq

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sanlorenzo

ASKER

here is teh code i develop , do you see any Problem , i try in any possible combination and it works
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click

If Me.ToolStripComboBox1.SelectedItem > "" And Me.ToolStripComboBox2.SelectedItem > "" Then

Dim MultyQuerry = From tbl_Name In db.tbl_Names _
Where tbl_Name.Continent = Me.ToolStripComboBox1.SelectedItem.ToString _
And tbl_Name.Country = Me.ToolStripComboBox2.SelectedItem.ToString _
Select tbl_Name
Me.Tbl_NameBindingSource.DataSource = MultyQuerry

End If
If Me.ToolStripComboBox1.SelectedItem > "" And Me.ToolStripComboBox2.SelectedItem = "" Then

Dim MultyQuerry1 = From tbl_Name In db.tbl_Names _
Where tbl_Name.Continent = Me.ToolStripComboBox1.SelectedItem.ToString _
Select tbl_Name

Me.Tbl_NameBindingSource.DataSource = MultyQuerry1
End If
If Me.ToolStripComboBox1.SelectedItem = "" And Me.ToolStripComboBox2.SelectedItem > "" Then

Dim MultyQuerry2 = From tbl_Name In db.tbl_Names _
Where tbl_Name.Country = Me.ToolStripComboBox2.SelectedItem.ToString _
Select tbl_Name
Me.Tbl_NameBindingSource.DataSource = MultyQuerry2
End If
If Me.ToolStripComboBox1.SelectedItem = "" And Me.ToolStripComboBox2.SelectedItem = "" Then

Dim MultyQuerry3 = From tbl_Name In db.tbl_Names

Select Case db.tbl_Names

End Select

Me.Tbl_NameBindingSource.DataSource = MultyQuerry3

End If

End Sub

sanlorenzo

ASKER

Is there any one to help , if for instance the Combo Box instead being 2 become 4 , i see i should have a better code to apply ???

Thanks