Binded text of text block ,save that text in a variable

Question

<TextBlock x:Name="t1" Grid.Row="0" Grid.Column="1" TextAlignment="Center" Text="{Binding Path=ECG}" Margin="55,22,10,2"/>

 

save the text on cs file (back end).

string i=t1. Text

 

 

its not identifying the t1 (textblock) in the current context