Naresh.Jois » LINQ2SQL

Use Debug output window to monitor SQL generated by LINQ2SQL

naresh — Mon, 28 Jun 2010 06:38:48 +0000

In all the examples out there to see the SQL generated by a LINQ2SQL query console.out is used, but to monitor the SQL in a debug window we need to write a special text writer implementation

using System.IO;
using System.Text;
using System.Diagnostics;
using System.Globalization;
using System;
namespace nj.Diagnostics
{
    /// 
    /// Implements a  for writing information to the debugger log.
    /// 
    /// 
    public class DebuggerWriter : TextWriter
    {
        private bool isOpen;
        private static UnicodeEncoding encoding;
        private readonly int level;
        private readonly string category;
 
        /// 
        /// Initializes a new instance of the  class.
        /// 
        public DebuggerWriter()
            : this(0, Debugger.DefaultCategory)
        {
        }
 
        /// 
        /// Initializes a new instance of the  class with the specified level and category.
        /// 
        /// A description of the importance of the messages.
        /// The category of the messages.
        public DebuggerWriter(int level, string category)
            : this(level, category, CultureInfo.CurrentCulture)
        {
        }
 
        /// 
        /// Initializes a new instance of the  class with the specified level, category and format provider.
        /// 
        /// A description of the importance of the messages.
        /// The category of the messages.
        /// An  object that controls formatting.
        public DebuggerWriter(int level, string category, IFormatProvider formatProvider)
            : base(formatProvider)
        {
            this.level = level;
            this.category = category;
            this.isOpen = true;
        }
 
        protected override void Dispose(bool disposing)
        {
            isOpen = false;
            base.Dispose(disposing);
        }
 
        public override void Write(char value)
        {
            if (!isOpen)
            {
                throw new ObjectDisposedException(null);
            }
            Debugger.Log(level, category, value.ToString());
        }
 
        public override void Write(string value)
        {
            if (!isOpen)
            {
                throw new ObjectDisposedException(null);
            }
            if (value != null)
            {
                Debugger.Log(level, category, value);
            }
        }
 
        public override void Write(char[] buffer, int index, int count)
        {
            if (!isOpen)
            {
                throw new ObjectDisposedException(null);
            }
            if (buffer == null || index < 0 || count < 0 || buffer.Length - index < count)
            {
                base.Write(buffer, index, count); // delegate throw exception to base class
            }
            Debugger.Log(level, category, new string(buffer, index, count));
        }
 
        public override Encoding Encoding
        {
            get
            {
                if (encoding == null)
                {
                    encoding = new UnicodeEncoding(false, false);
                }
                return encoding;
            }
        }
 
        public int Level
        {
            get { return level; }
        }
 
        public string Category
        {
            get { return category; }
        }
    }
}

The you can use

datacontext.log = new DebuggerWriter();

Cascade Delete with Linq2SQL

naresh — Tue, 22 Dec 2009 17:46:52 +0000

Consider this, you have Invoice and Invioce details in 2 tables and the details are referenced by InvoiceId, What happens to Invoice Details once you delete the invoice ?, In SQL atleast you can do cascade delete and also set the value to null, but most real life programs would want to delete the details, Linq2SQL by default tries to set a null value which in most cases fails, and there is no visual way to set this the only way to do this is to do some manual xml editing.
Right click and open the .dbml file with the XML Editor and then navigate to the table for which you want to do this, then look for the relation which references the parent table

 Name="...." Member="...." ThisKey="...." OtherKey="...." Type="...." IsForeignKey="true" />

Now add DeleteOnNull=”true” to this association so this behaves as expected

 Name="...." Member="...." ThisKey="...." OtherKey="...." Type="...." IsForeignKey="true" DeleteOnNull="true" />

LINQ2SQL RAD with confidence

naresh — Sat, 24 Jan 2009 07:22:07 +0000

If you are like me who also does have to done some rapid prototyping and application development, you know how painstaking it is to do setup each wire for even a simple application to work, and you will be working so rapidly that you would have forgotten the column names you have entered in db few minutes ago, that fact aside you would still require a large prieces of code which would actually constitute the middle tier of application, but the problem is in RAD you do need a top notch middle tier which would cover all the aspects required, then what ? and add to that the fact that you are so used to working with objects that you have even forgotten how to retrive data just using code or you find the whole connection – adapter – dataset thing too outdated and too much work just to retrive one row from db.

Now we know what a middle teir is , its nothing but an ORM which maps objects to data along with addtional functions to manipulate that data, for this there exists good amount of code generators which based on your database would generate all code required which would constitute the core of middle tier, but i always found them to be too cumberome ( may be i am too lazy) , now may be some year and a half ago , i was working on a project which extensively used LINQ for queying objects, instead of writing functions for each thing, till then LINQ has become second nature, and i wonder how i used to to do this when LINQ was not around, same time i started looking web for LINQ and i saw something about DLINQ which is now reffered to as LINQ2SQL, LINQ2SQL does what we need to do the hard way, wire up. Just create a new LINQ2SQL class in your project and drag the tables from Server Explorer and voila , you have your midddle tier ready (well not exactly) , it creates classes for each of the table in the db along with associations for relations , (eg : If i have a students table in it creates a student class with each column in student as a property, and if you have something like SectionId in Student which links to the section table you can access the linked section by just using Student.Section). Everything becomes so simple from here on, atleast for RAD, It also creates functions for SPs,

The only problem i have with this till date is it works only with SQL Server (I have been able to get it working with SQLCE – If this only worked with MySQL) and some things like serialization doesn’t happen the way i want it to , but anyway this is a tool which you have to use once to get know its usefullness.