WPF datagrid not showing data after binding it to LINQ join query resu

Question

I have a data grid in WPF that is populated from LINQ join query as follows:

public IEnumerable<InboxTransaction> GetAllInboxTransactions()
{
try
{
var result =
from s in this.InboxContext.Inboxes
join st in this.InboxContext.Sites
on s.Trans_Site equals st.Site_Code
select new InboxTransaction
(
s.Trans_Number,
s.Trans_Date,
s.Trans_Description,
st.Site_Description
);
return (result);
}
catch(Exception e)
{
MessageBox.Show("??? ??? ???");
throw (e);
}

When I bind the data grid to this result, data grid is not showing any data:

 

var source = InboxTrans.GetAllInboxTransactions();

InboxGrid.ItemsSource = source;

 

This is the definition of the data grid:

<DataGrid Name="InboxGrid" AutoGenerateColumns="False" CanUserAddRows="False" CanUserResizeColumns="True" DataContext="{Binding}" FlowDirection="RightToLeft" ItemsSource="{Binding}" Margin="5,94,42,218" Grid.ColumnSpan="3" Grid.Column="2">
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding Trans_Number}" Header="??? ??????" IsReadOnly="True" Visibility="Visible" />
<DataGridTextColumn Binding="{Binding Trans_Date}" Header="????? ??????" IsReadOnly="True" Visibility="Visible" />
<DataGridTextColumn Binding="{Binding Trans_Description}" Header="???? ??????" IsReadOnly="True" Visibility="Visible" />
<DataGridTextColumn Binding="{Binding Site_Name}" Header="????? ?????? ?????" IsReadOnly="True" Visibility="Visible" />
<DataGridTemplateColumn>
 <DataGrid Name="InboxGrid" AutoGenerateColumns="False" CanUserAddRows="False" CanUserResizeColumns="True"                  DataContext="{Binding}" FlowDirection="RightToLeft" ItemsSource="{Binding}" Margin="5,94,42,218" Grid.ColumnSpan="3" Grid.Column="2">
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding Trans_Number}" Header="??? ??????" IsReadOnly="True" Visibility="Visible" />
<DataGridTextColumn Binding="{Binding Trans_Date}" Header="????? ??????" IsReadOnly="True" Visibility="Visible" />
<DataGridTextColumn Binding="{Binding Trans_Description}" Header="???? ??????" IsReadOnly="True" Visibility="Visible" />
<DataGridTextColumn Binding="{Binding Site_Name}" Header="????? ?????? ?????" IsReadOnly="True" Visibility="Visible" />
<DataGridTemplateColumn> <DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Button x:Name="btnDelete" Click="btnDelete_Click" Content="???" />
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>