Finding maximum and minimum Value column wise in datatable

Question

I have two tables I want to compare them using Par Name column(here rows are compare with columns of table5) and find lowest and highest values 

table 1 

Par Name	SKIP	Lowest value	Highest Value
D_Id	0
Split	0
Val_2	0
Val_1	0
Val_4	0

table5 

D_ID	Split	Val_1	Val_2	Val_4
N_01	Ret	-0.13672	-0.56202	-0.4211
N_92	Ret	-0.13767	-0.13911	-0.56752
N_03	Stress	-0.13711	-0.42072	-0.41932
N_98	Stress	-0.6132	-0.41979	-0.42025
N_56	Stress	-0.42026	-0.41955	-0.1367

  for (int q = 2; q < table1.Rows.Count; q++)
            {


                string colVal = table1.Rows[q]["Par Name"].ToString(); 
                if(table5.Columns.Contains(colVal))
                {

// Error : Specified cast is not valid
 table1.Rows[q]["Lowest value"] = table5.AsEnumerable().Min(r => r.Field<double>(colVal));
 table1.Rows[q]["Highest Value"] = table5.AsEnumerable().Max(r => r.Field<double>(colVal));
                }
            }




output table

Par Name	SKIP	Lowest value	Highest Value
D_Id	0
Split	0
Val_2	0	-0.56202	-0.13911
Val_1	0	-0.6132	-0.13672
Val_4	0	-0.56752	-0.1367