When we are not sure whether the records in Table A will have matching records in Table B, we should use left join. Where left join and inner join are applied also play a vital role in query execution. Use of left join and inner join at the right places The variable will be used in the query execution and the query will be cached. SQL query generated will reserve a variable and hold a value. SQL query generated will use hard-coded value, so caching will not be applied. OFFSET ROWS FETCH NEXT ROWS ONLY When writing skip and take in LINQ queries, please consider the following for better performance: AvoidįileCollection.OrderBy(a=>a.Id).Skip(skip).Take(take) įileCollection.OrderBy(a=>a.Id).Skip(()=>skip).Take(()=>take) Return fileCollection.OrderBy(a=>a.Id).Skip(()=>skip).Take(()=>take).Select(a=>new Build queries dynamically over Queryable collectionįileCollection = fileCollection.Where(a => a.FileRevision = fileRevision & a.IsDeleted = false) įileCollection = fileCollection.Where(a => a.FileRevision = fileNumber & a.IsDeleted = false) IQueryable fileCollection = context.FileRepository Select and perform join on the needed tables and build an IQueryable collection The IQueryable type in C# can hold unevaluated SQL queries, which can later be converted to run against the data collection after applying skip and take.Ĭ# private IEnumerable LoadAllFiles(int skip, int take,string fileRevision,string fileNumber) When the user wants to see the next set of records, we can load the next 10 or 20 records on demand. Instead, we can load a certain number of records initially, say 10 or 20. When working with a large collection of data and binding it with a table or grid control, we should not load all records for the user in a single instance because it takes a long time. Query Compiled into More Efficient SQL Use of IQueryable and Skip/Take This query will be compiled into SQL in an optimized way as shown in the following screenshot. Var fileCollection = (a => a.IsDeleted = false). We can change the query as follows for better execution. This consumes more memory than necessary and slows down query execution. Though we might need only a few columns, we have loaded them all. This query will be compiled into SQL as shown the following screenshot. Var fileCollection = (a => a.IsDeleted = false).ToList() When working with LINQ, only pull the needed columns in the Select clause instead of loading all the columns in the table.Ĭonsider the following LINQ query. Use of left join and inner join at the right places.The following are a few things to consider when aiming to improve the performance of LINQ to Entities: There are certain techniques to follow when writing queries to make sure they run quickly and effectively.
C3 ef join objects from different contexts software#
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