EF数据Linq方式查询

            using (var ctx = new NorthwindEntities())
            {
                //单表查询SQL查询方式
                //SELECT * FROM Customers AS c WHERE c.City = 'London' AND c.CustomerID = 'EASTC'
                dataGridView1.DataSource = (from c in ctx.Customers where c.City == "London" && c.CustomerID == "EASTC" select c).ToList();

                //模糊查询
                //SELECT * FROM Customers AS c WHERE c.City LIKE 'L%'
                dataGridView1.DataSource = (from c in ctx.Customers where c.City.StartsWith("L") select c).ToList();
                //SELECT * FROM Customers AS c WHERE c.City LIKE '%L'
                dataGridView1.DataSource = (from c in ctx.Customers where c.City.EndsWith("L") select c).ToList();
                //SELECT * FROM Customers AS c WHERE c.City LIKE '%L%'
                dataGridView1.DataSource = (from c in ctx.Customers where c.City.Contains("L") select c).ToList();
                //SELECT * FROM Customers AS c WHERE c.City='London' ORDER BY c.CustomerID

                //排序
                //SELECT * FROM Customers AS c WHERE c.City='London' ORDER BY c.CustomerID
                dataGridView1.DataSource = (from c in ctx.Customers where c.City == "London" orderby c.CustomerID select c).ToList();

                //只查询部分列，并排序
                //SELECT c.CustomerID, c.CompanyName, c.ContactName FROM Customers AS c
                //WHERE c.CompanyName = 'The Big Cheese'
                //ORDER BY c.CompanyName
                dataGridView1.DataSource = (from c in ctx.Customers where c.CompanyName == "The Big Cheese" orderby c.CompanyName select new { c.CustomerID, c.CompanyName, c.ContactName }).ToList();

                //分组
                //SELECT c.City,COUNT(c.CompanyName) FROM Customers AS c GROUP BY c.City
                dataGridView1.DataSource = (from c in ctx.Customers group c by c.City into r orderby r.Count() descending select new { City = r.Key, Count = r.Count() }).ToList();
            }
        }

数据模型

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