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POHow to combine a multi-part LINQ to Entities query
 

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  1. POHow to combine a multi-part LINQ to Entities query
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    <p>I posted this code snippet over at Stack Exchange's <a href="http://codereview.stackexchange.com">Code Review</a> (beta) in order to obtain some feedback on how best to refactor a multi-part <code>LINQ</code> query.</p> <p>Being relatively new to <code>LINQ</code>, I'm not really sure where to begin with this query.</p> <p>If anybody could give me any advice on combining a few of the LINQ queries within the method, I'd appreciate it; especially the <strong><em>'exclude'</em></strong> IQueryable collections into the main query (see comments).</p> <p>The query is not particularly performant at the moment and any advice you could give in order to improve its performance from a code perspective would be appreciated. </p> <p>The comments received on Code Review were more architectural, however I'm not currently in a position where I can move anything to the database at this time.</p> <p>I appreciate it's a large method, but I've posted the whole lot to give context.</p> <p>Thanks in advance for any advice you're able to give.</p> <h1>The Method</h1> <pre><code> /// Get templates by username and company public List&lt;BrowsingSessionItemModel&gt; GetItemBrowsingSessionItems( int companyId, string userName, Boolean hidePendingDeletions, Boolean hideWithAppointmentsPending, Boolean hideWithCallBacksPending, int viewMode, string searchString, List&lt;int?&gt; requiredStatuses, List&lt;int?&gt; requiredSources, string OrderBy, BrowsingSessionLeadCustomField fieldFilter) { try { IQueryable&lt;Lead&gt; exclude1; IQueryable&lt;Lead&gt; exclude2; IQueryable&lt;Lead&gt; exclude3; //To prepare call backs pending if (hideWithCallBacksPending == true) { exclude1 = (from l1 in db.Leads where (l1.Company_ID == companyId) from l2 // Hiding Pending Call Backs in db.Tasks .Where(o =&gt; (o.IsCompleted ?? false == false) &amp;&amp; (o.TaskType_ID == (int)RecordEnums.TaskType.PhoneCall) &amp;&amp; (o.Type_ID == (int)RecordEnums.RecordType.Lead) &amp;&amp; (o.Item_ID == l1.Lead_ID) &amp;&amp; (o.Due_Date &gt; EntityFunctions.AddDays(DateTime.Now, -1)) ) select l1); } else { exclude1 = (from l1 in db.Leads where (0 == 1) select l1); } //To prepare appointments backs pending if (hideWithAppointmentsPending == true) { exclude2 = (from a1 in db.Leads where (a1.Company_ID == companyId) from a2 // Hiding Pending Appointments in db.Tasks .Where(o =&gt; (o.IsCompleted ?? false == false) &amp;&amp; (o.TaskType_ID == (int)RecordEnums.TaskType.Appointment) &amp;&amp; (o.Type_ID == (int)RecordEnums.RecordType.Lead) &amp;&amp; (o.Item_ID == a1.Lead_ID) &amp;&amp; (o.Due_Date &gt; EntityFunctions.AddDays(DateTime.Now, -1)) ) select a1); } else { exclude2 = (from a1 in db.Leads where (0 == 1) select a1); } //To prepare deletions if (hidePendingDeletions == true) { exclude3 = (from d1 in db.Leads where (d1.Company_ID == companyId) from d2 // Hiding Pending Deletions in db.LeadDeletions .Where(o =&gt; (o.LeadId == d1.Lead_ID)) select d1); } else { exclude3 = (from d1 in db.Leads where (0 == 1) select d1); } // MAIN QUERY &lt;-- IQueryable&lt;Lead&gt; list = (from t1 in db.Leads from t2 in db.LeadSubOwners .Where(o =&gt; t1.Lead_ID == o.LeadId &amp;&amp; o.Expiry &gt;= DateTime.Now) .DefaultIfEmpty() where (t1.Company_ID == companyId) where ((t2.Username == userName) &amp;&amp; (viewMode == 1)) || ((t1.Owner == userName) &amp;&amp; (viewMode == 1)) || ((viewMode == 2)) // Either owned by the user or mode 2 (view all) select t1).Except(exclude1).Except(exclude2).Except(exclude3); // Filter sources and statuses seperately if (requiredStatuses.Count &gt; 0) { list = (from t1 in list where (requiredStatuses.Contains(t1.LeadStatus_ID)) select t1); } if (requiredSources.Count &gt; 0) { list = (from t1 in list where (requiredSources.Contains(t1.LeadSource_ID)) select t1); } // Do custom field filter here if (fieldFilter != null) { string stringIntegerValue = Convert.ToString(fieldFilter.IntegerValue); switch (fieldFilter.FieldTypeId) { case 1: list = (from t1 in list from t2 in db.CompanyLeadCustomFieldValues .Where(o =&gt; t1.Lead_ID == o.Lead_ID &amp;&amp; fieldFilter.TextValue == o.LeadCustomFieldValue_Value) select t1); break; case 2: list = (from t1 in list from t2 in db.CompanyLeadCustomFieldValues .Where(o =&gt; t1.Lead_ID == o.Lead_ID &amp;&amp; stringIntegerValue == o.LeadCustomFieldValue_Value) select t1); break; default: break; } } List&lt;Lead&gt; itemsSorted; // Sort here if (!String.IsNullOrEmpty(OrderBy)) { itemsSorted = list.OrderBy(OrderBy).ToList(); } else { itemsSorted = list.ToList(); } var items = itemsSorted.Select((x, index) =&gt; new BrowsingSessionItemModel { Id = x.Lead_ID, Index = index + 1 }); return items.ToList(); } catch (Exception ex) { logger.Info(ex.Message.ToString()); return new List&lt;BrowsingSessionItemModel&gt;(); } } </code></pre>
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    1. COIt seems that your code is too complicated. It should be re-factored. I agree with you.
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    2. COWTF is this `where (0 == 1)`? You can define Excepts conditionally in the same way you build filters. Check executed SQL query and measure in management studio if SQL is performance issue.
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      1. USLadislav Mrnka
 

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