Hello,
Is there a way to build a linq query in order to use it later or to display/print it (and more specifically, the where clause) ?
A:
Linq cannot be displayed (AFAIK), if you mean 'linq2sql' query (qg. sql query built from linq), no, it cannot be printed out.
Yossarian
2009-09-10 13:22:25
myDataContext.GetCommand(query).CommandText ?
David B
2009-09-10 13:28:13
@David B: mea culpa. Thanks for correcting, I didnt knew about this.
Yossarian
2009-09-10 13:35:25
+1
A:
Isn't LINQ a .NET 3.5-feature?
edit:
http://msdn.microsoft.com/en-us/library/bb332048.aspx
--> LINQ is only available from .NET 3.5, so not 3.0 as the topicstarter asks.
edit2:
Ok, so the TS talks about C# 3.0, which comes with .NET 3.5.
Quite confusing.
Natrium
2009-09-10 13:23:28
Tag is for C#3.0 and that is the C# version that came with .NET 3.5. You doesn't deserve negative points for this IMO, though.
Petar Repac
2009-09-10 13:28:07
LINQ syntax in C# is a C# 3.0 feature. LINQ implementations are .NET 3.5 features. C# 3.0 released simultaneously with .NET 3.5
David B
2009-09-10 13:29:11
@Petar, these remarks should've been made as a comment, rather as an answer. It doesn't help the topic starter, it adds nothing but noise, and it's what comments are meant for...
Razzie
2009-09-10 13:41:39
+8
A:
What exactly is it you want? You can capture just the expression from the Where - something like:
Expression<Func<SomeType, bool>> predicate = row => row.IsActive
&& row.Color == "red";
Because this is going to an expression tree, there is a meaningful ToString().
If you want the SQL (etc), then that will be implementation-specific. For example, with LINQ-to-SQL you can use .Log - for example, ctx.Log = Console.Out;
If you want the predicate out of the middle of an IQueryable<T> feed, then that is much trickier...
Marc Gravell
2009-09-10 13:24:53
can i use an expression as a where clause ? eg : IEnumerable<User> users = from u in GetAllUsers() where myExpression select u . With my expression beeing Expression<Func<User, bool>> ?
Toto
2009-09-10 13:35:38
Note that if `GetAllUsers()` returns `IEnumerable<T>`, you'll need to use `.AsQueryable().Where(myExpression)`
Marc Gravell
2009-09-10 13:38:42
A:
You could look at System.Linq.Dynamic its a addon to linq to build dynamic where, orderby etc.
eg tblProduct.Where("product_id = @0", product_id)
That might be of some assistance.
Matthew Hood
2009-09-10 13:27:15
A:
Look at this example from MSDN:
// Lambda expression as executable code.
Func<int, bool> deleg = i => i < 5;
// Invoke the delegate and display the output.
Console.WriteLine("deleg(4) = {0}", deleg(4));
// Lambda expression as data in the form of an expression tree.
System.Linq.Expressions.Expression<Func<int, bool>> expr = i => i < 5;
// Compile the expression tree into executable code.
Func<int, bool> deleg2 = expr.Compile();
// Invoke the method and print the output.
Console.WriteLine("deleg2(4) = {0}", deleg2(4));
Dewfy
2009-09-10 13:27:45