LINQ Range Variable Problem

Date Published: 05 October 2010

LINQ Range Variable Problem

Ran into this issue last night and just figured it out. I have this code for a demo:

<span style="color: #0000ff">using</span> System;<br /><span style="color: #0000ff">using</span> System.Data.Objects;<br /><span style="color: #0000ff">using</span> System.Transactions;<br /><span style="color: #0000ff">using</span> ExtractTransformLoad.Domain;<br /><span style="color: #0000ff">using</span> Northwind.Entities;<br /><span style="color: #008000">//using System.Linq;</span><br /><br /><span style="color: #0000ff">namespace</span> ExtractTransformLoad<br />{<br />    <span style="color: #0000ff">public</span> <span style="color: #0000ff">class</span> SqlFreightByShipperRepository : IFreightByShipperRepository<br />    {<br />        <span style="color: #0000ff">public</span> <span style="color: #0000ff">void</span> DeleteAndInsert(DateTime runDate, FreightByShipper freightByShipper)<br />        {<br />            <span style="color: #0000ff">using</span> (var context = <span style="color: #0000ff">new</span> NorthwindEntities())<br />            <span style="color: #0000ff">using</span> (var scope = <span style="color: #0000ff">new</span> TransactionScope())<br />            {<br />                var summaryToDelete = (from freightSummary <span style="color: #0000ff">in</span> context.FreightSummaries<br />                                       <span style="color: #0000ff">where</span><br />                                           freightSummary.RunDate == runDate &&<br />                                           freightSummary.ShipperName == freightByShipper.ShipperName<br /><br />                                       select freightSummary);<span style="color: #008000">//.FirstOrDefault();</span><br />                context.DeleteObject(summaryToDelete);<br /><br />                var newFreightSummary = <span style="color: #0000ff">new</span> FreightSummary()<br />                                         {<br />                                             Freight = freightByShipper.Freight,<br />                                             RunDate = DateTime.Today,<br />                                             ShipperName = freightByShipper.ShipperName<br />                                         };<br />                context.FreightSummaries.AddObject(newFreightSummary);<br />                context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);<br />                scope.Complete();<br />            }<br />        }<br />    }<br />}

Now, in Visual Studio, it looks like this:

image

Hovering over freightSummary in the above LINQ query would reveal just

(range variable) ? freightSummary

image

A bunch of searching later didn’t much help, although this thread did put me on the right track just a moment ago. The trick, it turns out, is that I didn’t have the System.Linq namespace included (you can see above I just re-commented it out). If you include System.Linq, everything works as expected. Final code here:

<span style="color: #0000ff">using</span> System;<br /><span style="color: #0000ff">using</span> System.Data.Objects;<br /><span style="color: #0000ff">using</span> System.Transactions;<br /><span style="color: #0000ff">using</span> ExtractTransformLoad.Domain;<br /><span style="color: #0000ff">using</span> Northwind.Entities;<br /><span style="color: #0000ff">using</span> System.Linq;<br /><br /><span style="color: #0000ff">namespace</span> ExtractTransformLoad<br />{<br />    <span style="color: #0000ff">public</span> <span style="color: #0000ff">class</span> SqlFreightByShipperRepository : IFreightByShipperRepository<br />    {<br />        <span style="color: #0000ff">public</span> <span style="color: #0000ff">void</span> DeleteAndInsert(DateTime runDate, FreightByShipper freightByShipper)<br />        {<br />            <span style="color: #0000ff">using</span> (var context = <span style="color: #0000ff">new</span> NorthwindEntities())<br />            <span style="color: #0000ff">using</span> (var scope = <span style="color: #0000ff">new</span> TransactionScope())<br />            {<br />                var summaryToDelete = (from freightSummary <span style="color: #0000ff">in</span> context.FreightSummaries<br />                                       <span style="color: #0000ff">where</span><br />                                           freightSummary.RunDate == runDate &&<br />                                           freightSummary.ShipperName == freightByShipper.ShipperName<br /><br />                                       select freightSummary).FirstOrDefault();<br />                context.DeleteObject(summaryToDelete);<br /><br />                var newFreightSummary = <span style="color: #0000ff">new</span> FreightSummary()<br />                                         {<br />                                             Freight = freightByShipper.Freight,<br />                                             RunDate = DateTime.Today,<br />                                             ShipperName = freightByShipper.ShipperName<br />                                         };<br />                context.FreightSummaries.AddObject(newFreightSummary);<br />                context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);<br />                scope.Complete();<br />            }<br />        }<br />    }<br />}

I guess I’m spoiled by Resharper, which normally prompts me for any namespace it detects that I’m trying to use but haven’t yet included. It wasn’t until I added the .FirstOrDefault() that R# kicked in, and then for some reason it couldn’t automatically add the using statement for System.Linq, but once I did so by hand, the Range Variable problem disappeared.

Steve Smith

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Software Engineer

Steve is an experienced software architect and trainer, focusing currently on ASP.NET Core and Domain-Driven Design.


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