Question

我不会将SqlDependence设置为LINQ查询工作代码：

var product = new DataServiceCollection<Product>(target.Products.Expand("DCQuantities").Where(p => p.Sku == "JRSTEST1"));
product.First().DCQuantities[0].AvailableQuantity = 42;
var result = target.SaveChanges();

问题 -

let SetDependency (dc:DataContext) qr fn= 
    use con=new SqlConnection(dc.Connection.ConnectionString)
    con.Open()
    use cmd=new SqlCommand(dc.GetCommand(qr).CommandText,con)
    let dpn=new SqlDependency(cmd)
    let rec remover=lazy(con.Close()
                         dpn.OnChange.RemoveHandler hnd)
    and hnd=new OnChangeEventHandler(fun ob ev->remover.Force()
                                                fn ev)
    dpn.OnChange.AddHandler hnd
    cmd.ExecuteReader()|>ignore
    remover

//SetDependency sql.DataContext q (fun _ ->"Check..."|>Console.WriteLine)

let q=query{for s in sql.Stady do
            select s}
q|>string //or (dc:DataContext).GetCommand(q).CommandText

和好工作;

SELECT [t0].[Id], [t0].[Name], [t0].[PersonId], [t0].[AfterId] FROM [dbo].[Stady] AS [t0]

let q1=query{for s in sql.Stady do
             select s.Name}
q1|>string

和好工作;

SELECT [t0].[Name] FROM [dbo].[Stady] AS [t0]

let q2=query{for s in sql.Stady do select (s.Id,s.Name)} q2|>string (dc:DataContext).GetCommand(q2).CommandText

和

System.Linq.Enumerable+WhereSelectEnumerableIterator'2[Microsoft.FSharp.Linq.RuntimeHelpers.AnonymousObject'2[System.Int64,System.String],System.Tuple'2[System.Int64,System.String]]

和不工作

P.S。
DataContext.Loq写正确的查询 -

SELECT NULL AS [EMPTY]

从tupled linq查询中获取正确的sql命令

0 个答案: