Finding MAX and MIN based on Grouping in a DataTable

Question

//Edited
I have a DataTable, I want to Finding MAX and MIN based on Grouping in a DataTable.
Here in group column I want to Retain Max and Min value based on Group and delete rest in the same group
and when group is null just skip that row

Par Name	Group	Min	Max
ADC1	C_A	- 0.2	1
ADC2	C_A	- 2	2
USB1	C_R	-3	3
USB2	C_R	-4	2
Value1	C_A	-5	3
ADC3	C_A	-2	5
Value2		-4	1

Output : 

Par Name	Group	Min	Max
Value1	C_A	-5	3
ADC3	C_A	-2	5
USB2	C_R	-4	2
USB1	C_R	-3	3
Value		-4	1