WPF datagrid selection and selecteditem binding

Hi, I am not sure if I have enabled the selection mode, but I do have set selectionmode = single. But the selecteditem binding returns null every time. 

<DataGrid x:Name="dataGrid"  Grid.Column="1" Grid.RowSpan="1" Margin="0,0,0,0" VerticalAlignment="Top" SelectionMode="Single" ItemsSource="{Binding Collection.View}" AutoGenerateColumns="False" Height="Auto" Width="Auto" SelectedItem="{Binding Path=SelectedItem, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"><DataGrid.Columns><DataGridCheckBoxColumn/><DataGridTextColumn x:Name="Date" Binding="{Binding Path=VIQDATETIME}" Header="Date/Time" Width="Auto"/><DataGridTextColumn x:Name="CaseNumber" Binding="{Binding Path=COURTCASENUMBER}" Header="Case Number" Width="Auto"/><DataGridTextColumn x:Name="CaseCode" Binding="{Binding Path=CASECODE}" Header="Case Code" Width="Auto"/><DataGridTextColumn x:Name="Defendant" Binding="{Binding Path=LastName}" Header="Defendant" Width="Auto"/><DataGridTextColumn x:Name="Session" Binding="{Binding Path=SESSIONNAME}" Header="Session" Width="Auto"/><DataGridTextColumn x:Name="Node" Binding="{Binding Path=NodeID}" Header="Node" Width="Auto"/><DataGridTextColumn x:Name="Room" Binding="{Binding Path=COURTROOMNUMBER}" Header="Room" Width="Auto"/><DataGridTextColumn x:Name="CourtType" Binding="{Binding Path=CourtType}" Header="CourtType" Width="Auto"/></DataGrid.Columns></DataGrid>

 private EncryptionSearch _selectedItem;

        public EncryptionSearch SelectedItem
        {
            get { return _selectedItem; }
            set
            {
                _selectedItem = value;
                NoticeMe("SelectedItem");
            }
        }

        public void Encrypt()
        {
            using (var context = new CourtFLOWEntities())
            {
                try
                {
                    EncryptionRequest er = new EncryptionRequest
                    {
                        JobState = 0,
                        NodeID = _selectedItem.NodeID,
                        SessionName = _selectedItem.SESSIONNAME,
                        CaseCode = _selectedItem.CASECODE
                    };
                    context.EncryptionRequests.Add(er);
                }
                catch (Exception e)
                { MessageBox.Show(e.Message); }
            }
        }