Question

我正在尝试编写一个LINQ查询，该查询将在SQL之后呈现。我已经接近了，但仍然不正确。

所需的SQL

SELECT  

      TableDisplayColumns.Id
    , TableDisplayColumns.ViewName
    , TableDisplayColumns.ColumnName
    , TableDisplayColumns.ControllerName
    , TableDisplayColumns.TableDisplayName
    , TableDisplayColumns.IsVisibleByDefault

FROM dbo.TableDisplayColumns
LEFT JOIN dbo.UserTableDisplayColumns ON UserTableDisplayColumns.TableDisplayColumnId = TableDisplayColumns.Id

WHERE 
             (
                (TableDisplayColumns.IsVisibleByDefault = 1  AND UserTableDisplayColumns.IsNotVisible IS NULL)
                OR UserTableDisplayColumns.IsNotVisible = 0
             )
    AND (TableDisplayColumns.ControllerName = 'Contacts' AND TableDisplayColumns.ViewName = 'Index')

当前SQL

DECLARE @p0 NVarChar(1000) = 'Index'
DECLARE @p1 NVarChar(1000) = 'Contacts'
-- EndRegion
SELECT [t0].[Id], [t0].[ColumnName], [t0].[IsVisibleByDefault], [t0].[TableDisplayName], [t0].[ViewName]
FROM [TableDisplayColumns] AS [t0]
LEFT OUTER JOIN ([UserTableDisplayColumns] AS [t1]
    LEFT OUTER JOIN [TableDisplayColumns] AS [t2] ON [t2].[Id] = [t1].[TableDisplayColumnId]) ON [t0].[Id] = [t1].[TableDisplayColumnId]
WHERE ([t0].[ViewName] = @p0) AND ([t0].[ControllerName] = @p1) AND ([t0].[IsVisibleByDefault] = 1) AND ([t2].[IsVisibleByDefault] = 1)

实体

public class UserTableDisplayColumn
{
    public int Id { get; set; }

    public int TableDisplayColumnId { get; set; }

    public bool IsNotVisible { get; set; }

    public virtual TableDisplayColumn TableDisplayColumn { get; set; }
}

public class TableDisplayColumn
{

    public int Id { get; set; }

    [StringLength(50), Required]
    public string ViewName { get; set; }

    [StringLength(50), Required]
    public string ColumnName { get; set; }

    [StringLength(50), Required]
    public string ControllerName { get; set; }

    [StringLength(50), Required]
    public string TableDisplayName { get; set; }

    [Required]
    public bool IsVisibleByDefault { get; set; }
}

最后是当前查询：

    var query =  
            (
                from column in Context.TableDisplayColumns
                    .Where(x=>x.IsVisibleByDefault)
                    .Where(x=>x.ControllerName == "Contacts")
                    .Where(x=>x.ViewName == "Index")
                join userColumn in Context.UserTableDisplayColumns on column.Id equals userColumn.TableDisplayColumnId into userColumnColumns

                from userColumnColumn in userColumnColumns.DefaultIfEmpty()

                select new TableDisplayColumn()
                {
                    Id = column.Id,
                    ColumnName = column.ColumnName,
                    ControllerName = column.ColumnName,
                    IsVisibleByDefault = column.IsVisibleByDefault,
                    TableDisplayName = column.TableDisplayName,
                    ViewName = column.ViewName
                }
             ).ToList();

如果UsersColumns表中没有任何内容，我要完成的工作将获得默认列。如果UsersColumns中有记录，那么我只想在IsNotVisible = false时返回。

Answer 1

您可以使用let关键字以左连接方式引入集合。

var query =
  from x in Context.TableDisplayColumns
  where x.ControllerName == "Contacts"
  where x.ViewName == "Index"
  let ys = Context.UserTableDisplayColumns.Where(y => y.TableDisplayColumnId == x.Id)
  where (x.IsVisibleByDefault && !ys.Any()) || ys.Any(y => y.IsNotVisible == 0)
  select x;

创建具有多个where语句和左联接的linq查询

1 个答案: