Question

I have been working with a Linq query in a Silverlight application which returns only the row of a table which contains the max value of the field OptionARMRunId (identity). When executed in LinqPad, the query runs fine and returns the correct row. However, when used in my Silverlight application, the application never moves past the loading screen (while the status percentage goes to 100%, the blue circle continues to go around ad nauseam) and I receive an error in the browser. I have included the original Linq statement, the statement as it appears in my query, and the ie error below.

Linq statement (works correctly):

    from OptionARMProjection in OptionARMProjections.Where(row => row.OptionARMRunId == OptionARMProjections.Max(r => r.OptionARMRunId))
select OptionARMProjection

Linq statement in C# class (causes error when silverlight application is run):

    crocodileEntities proxy = new crocodileEntities(new Uri("CrocodileDbDataService.svc", UriKind.Relative));



    var ProjectionsQuery = from OptionARMProjections in proxy.OptionARMProjections.Where(row => row.OptionARMRunId == proxy.OptionARMProjections.Max(r => r.OptionARMRunId))
                            select OptionARMProjections;

Error received in ie8:

Webpage error details

User Agent: Mozilla/4.0 (compatible;
MSIE 8.0; Windows NT 6.1; Trident/4.0;
SLCC2; .NET CLR 2.0.50727; .NET CLR
3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2; Zune 4.0;
OfficeLiveConnector.1.4;
OfficeLivePatch.1.3; .NET4.0C;
.NET4.0E) Timestamp: Wed, 20 Jan 2010
03:06:13 UTC

Message: Unhandled Error in
Silverlight 2 Application The method
‘Max’ is not supported. at
System.Data.Services.Client.ResourceBinder.VisitMethodCall(MethodCallExpression
mce) at
System.Data.Services.Client.ExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.DataServiceExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.ExpressionVisitor.VisitBinary(BinaryExpression
b) at
System.Data.Services.Client.ResourceBinder.VisitBinary(BinaryExpression
b) at
System.Data.Services.Client.ExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.DataServiceExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.ExpressionVisitor.VisitLambda(LambdaExpression
lambda) at
System.Data.Services.Client.ExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.DataServiceExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.ExpressionVisitor.VisitUnary(UnaryExpression
u) at
System.Data.Services.Client.ExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.DataServiceExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.ExpressionVisitor.VisitExpressionList(ReadOnlyCollection1
original) at
System.Data.Services.Client.ExpressionVisitor.VisitMethodCall(MethodCallExpression
m) at
System.Data.Services.Client.ResourceBinder.VisitMethodCall(MethodCallExpression
mce) at
System.Data.Services.Client.ExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.DataServiceExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.ResourceBinder.AnalyzeProjection(MethodCallExpression
mce, Boolean matchMembers, Expression&
e) at
System.Data.Services.Client.ResourceBinder.VisitMethodCall(MethodCallExpression
mce) at
System.Data.Services.Client.ExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.DataServiceExpressionVisitor.Visit(Expression
exp) at
System.Data.Services.Client.ResourceBinder.Bind(Expression
e) at
System.Data.Services.Client.DataServiceQueryProvider.Translate(Expression
e) at
System.Data.Services.Client.DataServiceQuery1.get_QueryComponents()
at
System.Data.Services.Client.DataServiceRequest.CreateResult(Object
source, DataServiceContext context,
AsyncCallback callback, Object state)
at
System.Data.Services.Client.DataServiceQuery`1.BeginExecute(AsyncCallback
callback, Object state) at
OptionARMChart.OptionARMUniverse.GetOptionArmProjectionsASync()
at OptionARMChart.MainPage..ctor()
at
OptionARMChart.App.Application_Startup(Object
sender, StartupEventArgs e) at
MS.Internal.CoreInvokeHandler.InvokeEventHandler(Int32
typeIndex, Delegate handlerDelegate,
Object sender, Object args) at
MS.Internal.JoltHelper.FireEvent(IntPtr
unmanagedObj, IntPtr unmanagedObjArgs,
Int32 argsTypeIndex, String eventName)
Line: 1 Char: 1 Code: 0 URI:
http://localhost:5004/optionarmcharttestpage.aspx

Answer 1

.Max() isn’t supported, a workaround would be to do an reverse order and take the first:

var ProjectionsQuery = proxy.OptionARMProjections
                       .Where(row => row.OptionARMRunId == proxy.OptionARMProjections
                       .OrderByDescending(r => r.OptionARMRunId))
                       .Take(1);

Correction: Seems it is supported in Silverlight 3+, but it’s given me the same trouble more than once, so maybe someone can add some more details as to why.