Equivalent of SQL ISNULL in LINQ?

Question

In SQL you can run a ISNULL(null,'') how would you do this in a linq query?

I have a join in this query:

var hht = from x in db.HandheldAssets         join a in db.HandheldDevInfos on x.AssetID equals a.DevName into DevInfo         from aa in DevInfo.DefaultIfEmpty()         select new         {         AssetID = x.AssetID,         Status = xx.Online         }; 

but I have a column that has a bit type that is non nullable (xx.online) how can I set this to false if it is null?

Answer 1

Since aa is the set/object that might be null, can you check aa == null ?

(aa / xx might be interchangeable (a typo in the question); the original question talks about xx but only defines aa)

i.e.

select new {     AssetID = x.AssetID,     Status = aa == null ? (bool?)null : aa.Online; // a Nullable<bool> } 

or if you want the default to be false (not null):

select new {     AssetID = x.AssetID,     Status = aa == null ? false : aa.Online; } 

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Update; in response to the downvote, I've investigated more... the fact is, this is the right approach! Here's an example on Northwind:

        using(var ctx = new DataClasses1DataContext())         {             ctx.Log = Console.Out;             var qry = from boss in ctx.Employees                       join grunt in ctx.Employees                           on boss.EmployeeID equals grunt.ReportsTo into tree                       from tmp in tree.DefaultIfEmpty()                       select new                              {                                  ID = boss.EmployeeID,                                  Name = tmp == null ? "" : tmp.FirstName                         };             foreach(var row in qry)             {                 Console.WriteLine("{0}: {1}", row.ID, row.Name);             }         } 

And here's the TSQL - pretty much what we want (it isn't ISNULL, but it is close enough):

SELECT [t0].[EmployeeID] AS [ID],     (CASE         WHEN [t2].[test] IS NULL THEN CONVERT(NVarChar(10),@p0)         ELSE [t2].[FirstName]      END) AS [Name] FROM [dbo].[Employees] AS [t0] LEFT OUTER JOIN (     SELECT 1 AS [test], [t1].[FirstName], [t1].[ReportsTo]     FROM [dbo].[Employees] AS [t1]     ) AS [t2] ON ([t0].[EmployeeID]) = [t2].[ReportsTo] -- @p0: Input NVarChar (Size = 0; Prec = 0; Scale = 0) [] -- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 3.5.30729.1 

QED?

Answer 2

You can use the ?? operator to set the default value but first you must set the Nullable property to true in your dbml file in the required field (xx.Online)

var hht = from x in db.HandheldAssets         join a in db.HandheldDevInfos on x.AssetID equals a.DevName into DevInfo         from aa in DevInfo.DefaultIfEmpty()         select new         {         AssetID = x.AssetID,         Status = xx.Online ?? false         };