I have a C# datatable with below structure :

```
ProductID   PartNo   Grade1   Grade2   Grade3
Product1       P1      A       N/A      Z  
Product1       P2      B        E       Y 
Product1       P3      C        F       X 
Product2       P1      D       N/A      V   
Product2       P3     N/A       G       W 

```

I want to merge the datarows' value into 1 row by grouping product ID and Part No based on order of P1,P2,P3 (fixed list).The end format is P1\_P2\_P3 So the end result would be :

```
ProductID    PartNo        Grade1        Grade2     Grade3
Product1    P1_P2_P3        A_B_C        N/A_E_F     Z_Y_X  
Product2    P1_P2_P3      D_N/A_N/A     N/A_N/A_G   V_N/A_W  

```

Instead on foreach loop, is there any better way to achieve the end output thru C# LINQ ?