Posts tagged with c - page 6

LINQ to SQL template for Visual Studio 2008

A newer version of this LINQ to SQL template is available.

If you want to customize the LINQ to SQL code generation phase in your project without additional tool dependencies this could be what you’re looking for.

11 Dec 2008 Fixes to association code with one-to-one’s and with no serialization required. 7 Dec 2008 Added IsDelayLoaded, IsUnique. Fixed association code, stored proc update overrides. 17 Nov 2008 Added IsInheritanceDefault read/emit IsDefault on type 26 Oct 2008 Emit column Name attribute if it doesn’t match the member (thanks Steele) 20 Oct 2008 Handle class naming better, fix associations for renamed or out-of-sequence keys and their access modifiers 25 Sep 2008 Figure out missing association keys by using either sides primary key 25 Sep 2008 Empty DBML name-space is now no namespace instead of “MyApplication” 23 Sep 2008 fixed stored procedures with 0 parameters 22 Sep 2008 fixed VB.NET IsForeignKey attribute for associations 18 Sep 2008 now generates stored procedures including insert/update/delete with concurrency checking.

New since ‘reloaded’ version

  • Inheritance – generates sub-classes with all properties and code mappings.
  • VB.NETCSharpDataContext.tt is joined by a VB.NET emitting VBNetDataContext.tt.
  • DataContract SP1 – additional mode to emit SP1-compatible DataContract serialization via Roger Jennings.
  • Composite keys – both as the primary key and as a foreign key in an association.
  • Type attributes – the data context and entity types can now be sealed or abstract as well as public, private, protected, internal or protected internal.
  • Associations – prevents foreign key values changing once the object association is made and updates parent side of one-to-many associations.
  • Stored procedures – generates method wrappers and associated methods to facilitate insert/update/delete with concurrency support.

Functionality compared to designer

A primary goal in developing the template was to allow for easy switching between the template and the LINQ to SQL designer so things are very similar.

Missing

  • Comprehensive sanity checking on the DBML.
  • The Custom Tool Namespace and project namespaces are not pulled in when the DBML namespaces not specified.

Fixed

The designer has a few bugs which helpfully this template doesn’t suffer from.

  • Modifying a table via a stored procedure using original values for concurrency will throw ChangeConflictException and not silently fail.
  • Protected internal virtual property doesn’t forget to be virtual.
  • Checks all associations based on a foreign key are not loaded before allowing change and not just the first one.

Improved

  • Fully customizable with full source.
  • Serialization mode to support DataContract improvements in .NET 3.5 SP1 To use uncomment the line // data.Serialization = SerializationMode.DataContractSP1; in xDataClasses.tt
  • CanBeNull attribute generated for value types (useful when working with metadata).

Source compared to designer

The designer generated code can be difficult to read and isn’t well suited to template generation so the output from this template is different in a number of ways:

Sequence

Everything related to a column mapping – the storage variable, event signatures, attribute and the property itself – is batched together so it can be hit with a single loop making the template shorter and easier to work with.

#regions

Opinion may be divided on the usefulness of #regions in your own code but for code generation of large files I found it invaluable. There are regions for the logical parts of the data context and within each entity such as construction, column mapping, associations and serialization.

Style

The code generated should be a little easier to follow – if/else ordering, no redundant casts or extra brackets etc.

Namespace

I don’t believe adding “this” everywhere or fully qualifying attributes and exceptions makes things easy to read. I realize this might cause some name conflicts for some people but it is easy to change yourself and means the code is shorter and easier to work with for the majority.

Getting started

Although I work on the LINQ to SQL team this template should be treated as a third-party sample and is not supported by Microsoft.

Download via CodePlex

  1. Add the L2ST4.ttinclude and either CSharpDataContext.tt or VBNetDataContext.tt to your project depending on your language type
  2. Rename the xDataContext.tt to match your DBML file but with .tt extension instead of .dbml
  3. Set the existing DBML file’s .designer.cs/vb Build Action property to None to ignore the LINQ to SQL built-in code generation

Note that the template will only regenerate when it has been changed so use Run Custom Tool from the template’s right-mouse button menu in Solution Explorer when you’ve changed the DBML.

Should you wish to switch back to using the designer code then set the DBML file’s .designer.cs/vb Build Action to Compile and either remove the .tt and .ttinclude file for permanent removal or just set the .generated.cs/vb Build Action to None to keep it around. VB.NET users will need to use Show All Files to see the .designer.vb file.

Customization

The template run-time built into Visual Studio 2008 is called T4 and requires no additional tools however if you do a lot of editing you might want to install the Clarius T4 Editor for syntax highlighting and also check out the treasure trove of T4 material that is Oleg Sych’s blog.

The template is simple to follow, it loads the DBML file as an XML document then uses LINQ to XML to instantiate wrapper objects over the elements. This gives you a simple way to change default naming and behavior while making the template simpler to work with.

Let me know how you get on by leaving a comment here.

[)amien

LINQ to SQL log to debug window, file, memory or multiple writers

The Log property on a LINQ to SQL data context takes a TextWriter and streams out details of the SQL statements and parameters that are being generated and sent to the server.

Normally in examples you will see Console.Out being assigned to it which is fine for small demos and sandboxes but sooner or later you’ll want access to it in Windows or web applications. Here are some examples of how to redirect TextWriter output such as the DataContext log to other destinations.

Github has the latest version of ActionTextWriter etc.

To the output/debug window

The output/debug window mechanism actually uses a listener mechanism and so doesn’t actually directly expose a TextWriter interface however we can simply wrap up Debug.Write in something that does and use that instead:

class DebugTextWriter : System.IO.TextWriter {
   public override void Write(char[] buffer, int index, int count) {
       System.Diagnostics.Debug.Write(new String(buffer, index, count));
   }

   public override void Write(string value) {
       System.Diagnostics.Debug.Write(value);
   }

   public override Encoding Encoding {
       get { return System.Text.Encoding.Default; }
   }
}

To use it then simply:

myDataContext.Log = new DebugTextWriter();

To a file

#if DEBUG
 db.Log = new System.IO.StreamWriter("linq-to-sql.log") { AutoFlush = true };
#endif

If you wish to not overwrite the existing log file then change the constructor to include the parameter true after the filename. Bear in mind this log file can get very large and slow down your application with all that extra writing to disk and could well reveal information you’d rather wasn’t persisted there so the DEBUG conditional is recommended.

To memory

#if DEBUG
 var sw = new System.IO.StringWriter();
 db.Log = sw;
#endif

You will be able to examine sw or call ToString() on it to see the contents. Again this is not recommended for production as it will cause a lot of memory consumption as the StringWriter gets larger and larger.

To multiple writers

Here is a small useful class that lets you send the results intended for a TextWriter off into multiple writers.

class MulticastTextWriter : TextWriter {
  private readonly IList<TextWriter> textWriters;

  public MulticastTextWriter() : this(new List<TextWriter>()) {
  }

  public MulticastTextWriter(IList<TextWriter> textWriters) {
    this.textWriters = textWriters;
  }

  public void Add(TextWriter textWriter) {
    lock (textWriters)
      textWriters.Add(textWriter);
  }

  public bool Remove(TextWriter textWriter) {
    lock (textWriters)
      return textWriters.Remove(textWriter);
  }

  public override void Write(char[] buffer, int index, int count) {
    lock (textWriters)
      foreach (TextWriter textWriter in textWriters)
        textWriter.Write(buffer, index, count);
  }

  public override Encoding Encoding {
    get { return System.Text.Encoding.Default; }
  }
}

So if you wanted to output to a log and also to the debug window, you would use it like this (again recommended only for debugging):

var mw = new MulticastTextWriter();
mw.Add(new DebugTextWriter());
mw.Add(new System.IO.StreamWriter("linq-to-sql.log") { AutoFlush = true });
db.Log = mw;

Anything you want

To wrap things up here is a small TextWriter that lets you go off and do whatever you like with the string via the Action delegate.

class ActionTextWriter : TextWriter {
  private readonly Action<string> action;

  public ActionTextWriter(Action<string> action) {
    this.action = action;
  }

  public override void Write(char[] buffer, int index, int count) {
    Write(new string(buffer, index, count));
  }

  public override void Write(string value) {
    action.Invoke(value);
  }

  public override Encoding Encoding {
    get { return System.Text.Encoding.Default; }
  }
}

So if you wanted to output all log information to say a WinForms message box a tiny lambda expression gets you there:

db.Log = new ActionTextWriter(s => MessageBox.Show(s));

Have fun!

[)amien

LINQ to SQL T4 template reloaded

A newer version of this LINQ to SQL template is available.

The topic of modifying the code generation phase of LINQ to SQL comes up quite often and the limited T4 template I published here last month was good at showing the potential but wasn’t a practical replacement for the code generation phase.

I am please to make available the next version, which now…

  • Runs from the DBML therefore keeping the designer in the loop
  • Generate all the attributes for columns and tables including UpdateCheck, IsDbGenerated etc.
  • Supports associations including those with a foreign key
  • Generates appropriate attributes and code for both serialization modes

In short it generates code that is now functionally equivalent to SQL Metal with the following caveats:

  • C# only – VB.NET can be added if there is some interest
  • Stored procedures – not yet supported
  • Table inheritance – incomplete
  • DBML changes require you open and re-save the T4 template so it regenerates the code
  • Unidirectional serialization requires you add System.Runtime.Serialization to your project references (thanks Roger!)

To use the template:

  • Extract the archive and add the two files to your project
  • Right-click on the L2ST4.tt file, choose Properties and set the Custom Tool to blank
  • Rename DataClasses1.tt to the same name as your DBML file (but keeping the .tt extension) and open it
  • Click save and watch a freshly generate C# DataContext pop out
  • Switch off the LINQ to SQL designer generated C# by either setting the Custom Tool on the DBML to blank or setting the Build Action on the generated C# to None.

L2ST4.tt contains a lightweight wrapper around the DBML which is processed using LINQ to XML making the template easier to work with and providing a central for naming rules etc.

This code should be treated as a sample and hasn’t received much testing yet so feel free to leave comments or feedback here.

Some places you could take this template:

  • Generate an interface for your data context to improve mocking
  • Alternative naming and defaults
  • Splitting output into multiple files
  • New languages

[)amien

From the vaults of Twitter

I don’t normally republish my Tweets but are my highlights.

damienguard:
Methods returning “this” is a hack for fluency. Let’s get “..” added to the C# compiler to operate on previous object. a.This()..That()

lazycoder:
@damienguard I can’t decide if that’s genius or insanity. Should we add the “~” operator to refer back to the top of the inherit. chain? ;)

LostInTangent:
@damienguard I’ve started using Envy Code R for most of my applications (not just VS) and I have to say I’m loving it.

damienguard:
@LostInTangent: Envy Code R PR8 soon – Greek chars, improved hinting and some glyph revisions subscript/fractions & *96 redone.

damienguard:
Statically typed languages are not flexible enough to develop dynamically linked libraries.

damienguard:
Renaming your WiFi router StupidRouter does not alas shame it into being more reliable.

damienguard:
@command_tab: Am I the only one who finds paying for pretty UI’s to leverage free software that took much more effort to develop offensive?

damienguard:
Just took delivery on my Alps-switched keyboard… feels good so far… but let’s see if co-workers complain about the noise.

Plip:
@damienguard I CAN’T HEAR MYSELF THINK FOR THAT INFERNAL CLICKING !

damienguard:
@lancefisher The alps keyboard was from DSI USA… but don’t order one, terrible 2-key limits prevent fast typing.

damienguard:
Apple should add hobbyist to its OS X line-up. Make kernel easier to switch, remove the h/w lock-down and no support.

damienguard:
Standard windows font smoothing’s real problem is lack of scales. Convert a ClearType rendering to greyscale in Photoshop…

[)amien