{"id":645,"date":"2009-05-25T14:29:00","date_gmt":"2009-05-25T14:29:00","guid":{"rendered":"\/blogs\/bobb\/post\/L2S-and-EF-parameterization-problem-fixed-in-NET-40-almost.aspx"},"modified":"2013-01-03T23:59:45","modified_gmt":"2013-01-04T07:59:45","slug":"l2s-and-ef-parameterization-problem-fixed-in-net-4-0-almost","status":"publish","type":"post","link":"https:\/\/www.sqlskills.com\/blogs\/bobb\/l2s-and-ef-parameterization-problem-fixed-in-net-4-0-almost\/","title":{"rendered":"L2S and EF parameterization problem fixed in .NET 4.0 – almost"},"content":{"rendered":"

\nOne of the first things that I did after installing VS2010 beta this week was to check on a parameterization problem with string parameters, and Linq To SQL\/ADO.NET Entity Framework generated code. In the original version, this L2S query:\n<\/p>\n

\nvar x = from a in ents.authors
\n        where a.au_lname == "Smith"
\n        select new { a.au_lname, a.au_fname };\n<\/p>\n

\nor this EF query:\n<\/p>\n

\nstring name = "Smith";
\nvar x = from a in ents.authors
\n        where a.au_lname == name
\n        select new { a.au_lname, a.au_fname };\n<\/p>\n

\nWould cause plan cache pollution and possibly performance problems. These queries produced a query plan with the parameter specified as NVARCHAR(5). Each query with a different length will produce a new plan in the cache, and the use of NVARCHAR rather than VARCHAR will cause a table scan (rather than a seek) in the plan, regardless of how many rows are in the table, because there must be a conversion of au_lname from VARCHAR to NVARCHAR as part getting the rows, making the query non-sargable. The correct database data type (VARCHAR) needs to be specified as the parameter data type.\n<\/p>\n

\nIn .NET 4.0\/VS2010 Beta 1, L2S handles this, producing a VARCHAR(8000) parameter, as SQL Server's autoparameterization does. Entity Framework produces NVARCHAR(4000), fixing the length problem but still using the a different data type than the table specifies.\n<\/p>\n

\nNOTE: This will<\/strong> be fixed in the next beta version of .NET 4.0 to produce VARCHAR(8000). See complete post here<\/a>.\n<\/p>\n

\nIn my next installment of my MSDN "Under The Table", I'll be writing about the performance implications of data access method code in detail. I do mention "fixed in the next release" WRT L2S and EF, and hope that it will be resolved before .NET 4.0 ships.<\/p>\n","protected":false},"excerpt":{"rendered":"

One of the first things that I did after installing VS2010 beta this week was to check on a parameterization problem with string parameters, and Linq To SQL\/ADO.NET Entity Framework generated code. In the original version, this L2S query: var x = from a in ents.authors         where a.au_lname == "Smith"         select new { […]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[],"class_list":["post-645","post","type-post","status-publish","format-standard","hentry","category-data-access"],"yoast_head":"\nL2S and EF parameterization problem fixed in .NET 4.0 - almost - Bob Beauchemin<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.sqlskills.com\/blogs\/bobb\/l2s-and-ef-parameterization-problem-fixed-in-net-4-0-almost\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"L2S and EF parameterization problem fixed in .NET 4.0 - almost - Bob Beauchemin\" \/>\n<meta property=\"og:description\" content=\"One of the first things that I did after installing VS2010 beta this week was to check on a parameterization problem with string parameters, and Linq To SQL\/ADO.NET Entity Framework generated code. 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