Help processing checked treenodes in c# ASP.NET

I have a treeview that has three tiers.

The root node represents and areas
The roots child node represents rows within the areas
And the third tier child nodes represent plots within the rows

The Treeview is checkbox enabled.

The nodes values are long integers that correlate to id fields in tables.

The nodes text fields would be hierarchically
“Area (string value)”
“Row (string value)”
“Plot (string value)”

A layout of a sample treeview might look like this for the text

Area A
      Row 1
            Plot 1
            Plot 2
      Row 2
            Plot 1
            Plot 2
Area B
      Row 1
            Plot 1
            Plot 2
 
The treeview’s node values might look like this

1
      1
            1
            2
      2
            3
            4
2
      3
            5
            6

On a button click event I need to be able to process all the nodes to capture the values of checked nodes so I can insert them into a data table associated with their appropriate values…the table would read like this
AreaID      | RowID | PlotID

1      | 1           | 1
1      | 1           | 2
1      | 2           | 3
1      | 2         | 4
2      | 3         | 5
2      | 3         | 6

That is of course assuming that each node is checked.

I can work out the code for dealing with the database itself but I am totally at a loss how to go about processing each node to determine if it is checked or not for the purpose of setting the appropriate node to its correct field.

What I mean is I need to be able to cycle through all of the nodes and depending on the hierarchical node relationship and set its value to a variable of the appropriate type to insert into the data table.

Anyone able to help me come up with the best process to do this in c#