First you need to split the string to arrays for the validation.
string STR="0004168858,AB0688120881,15,PLATE CLAMPING CO,KTL 16,CEQP,GI31,1111,DV1111,22222222";
string[] strArrays = STR.Split(',');
Now you have list of values in the 'strArrays', and you can validate the fields using foreach (or) for loop iterations.
foreach(string st in strArrays)
{
st
}
OR
for(int i=0;i<strarrays.count;i++)>
{
strArrays[i]
}