c# - Entity Framework 中的联合或连接自定义数据

Question

嗨，我只是想在 sql 中像这样

SELECT ID,Name
FROM Countrys
UNION all
SELECT '00000000-0000-0000-0000-000000000000','All' Name
ORDER BY Id

将它与组合框上的“ALL”选项一起使用

using (GezentiEntities GE = new GezentiEntities())
{
    string[,] str = new string [1,2]{ {"00000000-0000-0000-0000-000000000000", "All"} };
    var obj = str.Cast<object>().ToArray();
    var countries = (from c in GE.Countrys select new { c.Id, c.Name })
                    .Concat
                    (from s in obj select s);

     cmbNationality.DataSource = countries.ToList();
     cmbNationality.ValueMember = "Id";
     cmbNationality.DisplayMember = "Name";
}

它给了我那个错误:

Unable to create a constant value of type 'System.Object'. Only primitive types or enumeration types are supported in this context.

Answer 1

只需将您的匿名类型查询放入一个列表中，然后使用列表的 add 方法追加一个匿名类型。

注意选择中变量的命名以及添加中的后续命名，以确保它们全部匹配。

var countries = (from c in GE.Countrys 
                 select new {Id = c.Id,Name = c.Name}).ToList();

countries.Add(new {Id = "00000000-0000-0000-0000-000000000000", Name = "All"});