(精华)2020年8月19日 数据库设计 EF增删改查语句

in 查询

var list = dbContext.Users.Where(u => new int[] { 1, 2, 3, 5, 7, 8, 9, 10, 11, 12, 14, 17 }.Contains(u.Id));//in查询
foreach (var user in list)
{
    Console.WriteLine(user.Name);
}

 var list = from u in dbContext.Users
            where new int[] { 1, 2, 3, 5, 7, 8, 9, 10, 11, 12, 14 }.Contains(u.Id)
            select u;

foreach (var user in list)
{
    Console.WriteLine(user.Name);
}

排序，分页

var list = dbContext.Users.Where(u => new int[] { 1, 2, 3, 5, 7, 8, 9, 10, 11, 12, 14, 18, 19, 20, 21, 22, 23 }.Contains(u.Id))
                          .OrderBy(u => u.Id)
                          .Select(u => new
                          {
                              Account = u.Account,
                              Pwd = u.Password
                          }).Skip(3).Take(5);
foreach (var user in list)
{
    Console.WriteLine(user.Pwd);
}

var list = (from u in dbContext.Users
           where new int[] { 1, 2, 3, 5, 7, 8, 9, 10, 11, 12, 14 }.Contains(u.Id)
            orderby u.Id
            select new
            {
                Account = u.Account,
                Pwd = u.Password
            }).Skip(3).Take(5);

foreach (var user in list)
{
    Console.WriteLine(user.Account);
}

多条件

var list = dbContext.Users.Where(u => u.Name.StartsWith("小") && u.Name.EndsWith("新"))
                          .Where(u => u.Name.EndsWith("新"))
                          .Where(u => u.Name.Contains("小新"))
                          .Where(u => u.Name.Length < 5)
                          .OrderBy(u => u.Id);

foreach (var user in list)
{
   Console.WriteLine(user.Name);
}

链接查询

var list = from u in dbContext.Users
           join c in dbContext.Companies on u.CompanyId equals c.Id
           where new int[] { 1, 2, 3, 4, 6, 7, 10 }.Contains(u.Id)
           select new
           {
               Account = u.Account,
               Pwd = u.Password,
               CompanyName = c.Name
           };//).Skip(3).Take(5);
foreach (var user in list)
{
    Console.WriteLine("{0} {1}", user.Account, user.Pwd);
}

var list = from u in dbContext.Users
           join c in dbContext.Categories on u.CompanyId equals c.Id
           into ucList
           from uc in ucList.DefaultIfEmpty()
           where new int[] { 1, 2, 3, 4, 6, 7, 10 }.Contains(u.Id)
           select new
           {
               Account = u.Account,
               Pwd = u.Password
           };
foreach (var user in list)
{
    Console.WriteLine("{0} {1}", user.Account, user.Pwd);
}

EF执行SQL语句

DbContextTransaction trans = null;
try
{
    trans = dbContext.Database.BeginTransaction();
    string sql = "Update [User] Set Name='小新' WHERE Id=@Id";
    SqlParameter parameter = new SqlParameter("@Id", 1);
    dbContext.Database.ExecuteSqlCommand(sql, parameter);
    trans.Commit();
}
catch (Exception ex)
{
    if (trans != null)
        trans.Rollback();
    throw ex;
}
finally
{
    trans.Dispose();
}

DbContextTransaction trans = null;
try
{
    trans = dbContext.Database.BeginTransaction();
    string sql = "SELECT * FROM [User] WHERE Id=@Id";
    SqlParameter parameter = new SqlParameter("@Id", 1);
    List<User> userList = dbContext.Database.SqlQuery<User>(sql, parameter).ToList<User>();
    trans.Commit();
}
catch (Exception ex)
{
    if (trans != null)
        trans.Rollback();
    throw ex;
}
finally
{
    trans.Dispose();
}