Generally we found that we make operations on dataset by getting values from table like searching, deleting ,updating but .net applications may generate error that table doesnt have primary key because for searching, deleting ,updating there should be primary key in table,
Our table has primary key but why this error get raised because our keys present in tables cant come directly into dataset we need to write
da(data adapter object).missingschemaaction=missingschema.addwithkey
This will get your tables in dataset along with keys.