var dynTable = "adfk234jk";
var dynFields = new String[] { "sdkksdfkl32wef", "ejwejiwi234ref" };

var sqlQuery = "select ";
for (int i = 0; i < dynFields.Length; i++)
    sqlQuery += (i == 0 ? "" : ",") + dynFields[i];
sqlQuery += " from " + dynTable;

var results = db.ExecuteQuery<MyDynClass>(sql);