Browse by Tags

Just a link from me at the moment but there’s a preview of the “Astoria Offline” work that was shown at the PDC now available from here I’m hoping to get time to download it and take a look at it in the near future.

Someone asked me if I had a simple sample of how to read/write documents into a database table using FILESTREAM in SQL Server 2008. I set about it. Firstly, I had to find out how to switch FILESTREAM on in the RTM of SQL Server. At times like this you need Bob Beauchemin to tell you how it's done and then you can go and run code such as this once you've done the necessary bits in SQL Configuration manager; exec sp_configure filestream_access_level, 2 reconfigure go CREATE DATABASE Documents ON PRIMARY ( NAME = DocData, FILENAME = 'c:\temp\docs.mdf' ), FILEGROUP FileGroup CONTAINS FILESTREAM ( NAME = DocFiles, FILENAME = 'c:\temp\docstreams' ) LOG ON ( NAME = DocLog, FILENAME = 'c:\temp\docs.ldf' ) GO and now I've got a database that can accept file stream data. Phew. Time for a simple table; create table Docs ( id uniqueidentifier rowguidcol not null primary key , documentData varbinary( max ) filestream not null , documentName nvarchar(1024) not null ) Now I've got a table I can use something like Windows Presentation...

This is similar but not at all identical to this post about LINQ to SQL because it's using a different framework and that has different capabilities. Someone mailed and asked how we can detect concurrency problems with Entity Framework in order to ensure that when we submit changes to the DB we first; Present the user with a list of all the concurrency errors in one go Present the user with their changes versus the DB's current data Ask the user how to go about resolving each issue Repeat until all the changes get to the DB one way or another I can use the same tables and scripts and so on that I used in the previous post about LINQ to SQL. So...if I've got this table in my DB; create table Person ( id int identity primary key , firstName nvarchar(30), lastName nvarchar(30), timestamp ) with data; insert person(firstname,lastname) values ( 'first1' , 'last1' ) insert person(firstname,lastname) values ( 'first2' , 'last2' ) insert person(firstname,lastname) values ( 'first3' , 'last3' ) and I bring this into an...

Following on from this last post , if I start to edit the data in the grid and change some value then the property value will change in the underlying class but nothing else will happen. That is, the NorthwindEntities class which is managing my data for me client-side ( which is derived from DataServiceContext ) isn't going to be aware of those modifications. Why not? If we have a look at a property on a generated class such as this one for the CompanyName on the Customers class; public string CompanyName { get { return this ._CompanyName; } set { this .OnCompanyNameChanging( value ); this ._CompanyName = value ; this .OnCompanyNameChanged(); } } Now, OnCompanyNameChanging and OnCompanyNameChanged are partial methods with no implementation by default so nothing's going to happen when something like the DataGrid changes a value such as CompanyName. Similarly, the generated entity classes such as Customers do not implement INotifyPropertyChanged which means that changes in the data will not be reflected in the UI...

Someone asked me today how you'd go about ensuring that timestamp columns in your database tables show up in your Entity Framework EDMX file with a Concurrency=Fixed attribute on them. That is - it's very likely that the timestamps are there on the table to enforce concurrency so why not default their Concurrency value to "Fixed" ? It's a good question but it's not something that the tooling does as far as I'm aware so I tried to have together some LINQ to XML code that would make an attempt at it. I don't claim that this is correct at all but it might be a starting point for this and similar, related pre-processing that you want to do on an EDMX file. static void Main( string [] args) { XElement edmxFile = XElement.Load(args[0]); XNamespace edmxNs = XNamespace.Get( "http://schemas.microsoft.com/ado/2007/06/edmx" ); XNamespace ssdlNs = XNamespace.Get( "http://schemas.microsoft.com/ado/2006/04/edm/ssdl" ); XNamespace mapNs = XNamespace.Get( "urn:schemas-microsoft-com:windows:storage:mapping:CS" ); XNamespace csdlNs...

Something that I came across today - if you're trying to surface a LINQ to SQL data source via the latest build of ADO.NET Data Services and you're running datasvcutil.exe on the metadata of the service then you might find yourself with a whole bunch of errors. Here's a sample of what I was getting this morning; error 7001: Schema specified is not valid. Errors: $metadata(0,0) : error 0005: The 'Namespace' attribute is invalid - The value '' is invalid according to its datatype ' http://schemas.microsoft.com/ado/2006/04/ edm:TNamespaceName' - The Pattern constraint failed. For me, I resolved this by just making sure that I revisited my DBML diagram for LINQ to SQL in Visual Studio and set the "Entity Namespace" property for code generation. That is, click on the white-space of the diagram; to make sure that you have the diagram rather than a particular entity set selected. Then hit F4 for the properties; and give yourself a namespace and all the errors seem to go away reasonably quickly :-)

Just like for batching, there's a great explanation of how concurrency looks in ADO.NET Data Services up here so this is just a basic example. If I take the "Hello World" style service that I built back here then it does nothing about concurrency checking because, by default, when you build an entity data model with the Entity Framework tooling all of the concurrency options are set to "off". So, if I make a request for a customer and trace it with Fiddler then I see; You can see that I'm requesting the ALFKI customer and I'm just doing it from a browser as it happens. Now, if I go and alter my entity data model a little bit to say that ( purely for instance ) I want to have concurrency checking done on the PostalCode, Country, Region, Address fields of the Customers entity type as in; Then the next time I request that entity I see an ETag header being emitted that contains the value of my concurrency token; and if I was to request lots of customers then I'd see these ETags move into the response data as in; From...