linq经验集合

整理中。。。。。

1.多id查询

var queryable = from c in this.db.NewsInfo where "9,10,11,12,13".Split(',').Contains(c.SmallId) orderby c.id descending select c;

 2.linq 简单操作datatable

var result1 = (from row in datatable.AsEnumerable()
                   select row["c1"].ToString()).ToList();
 
result1.AddRange(
                              (from row2 in datatable.AsEnumerable()
                             select row2["c2"].ToString()).toArray()
                            );
 
string[] arrays = result1.ToArray();

 3.通过查询排序号的集合中的某一值得索引位置

List<Student> studentsIndex = new List<Student>();
studentsIndex.Add(new Student { Id = 101, StudentName = "达一", Birthday = DateTime.Now });
studentsIndex.Add(new Student { Id = 102, StudentName = "坤二", Birthday = DateTime.Now });
studentsIndex.Add(new Student { Id = 103, StudentName = "坤三", Birthday = DateTime.Now });
var index_string_query = studentsIndex.Select((person, index) => new { index, person.StudentName }).OrderBy(i => i.StudentName);
var indexName = from c in index_string_query where c.StudentName=="坤三" select c; 
            //foreach (var item in index_string_query)
            //{
            //    Console.WriteLine(item.index + ":" + item.StudentName);
            //}
            Console.WriteLine(indexName);