New "dynamic" Keyword in C# 4

Instead of doing this:

object calc = GetCalculator();
Type calcType = calc.GetType();
object res = calcType.InvokeMember("Add",
    BindingFlags.InvokeMethod, null,
    new object[] { 10, 20 });
int sum = Convert.ToInt32(res);

Do this now:

dynamic calc = GetCalculator();
int sum = calc.Add(10, 20);

Thanks to Scott Hanselman by his post.

Avoid mercurial auto merge

Just put this in mercurial.ini :

[ui]
merge=kdiff3

[merge-tools]
kdiff3.premerge=false
kdiff3.args=--L1 base --L2 local --L3 other $base $local $other -o $output

How to prevent automatic MSDTC promotion

SQL Server 2005 (and maybe others) automatically promotes its connection to MSDTC when using TransactionScope.
To avoid this, set the connection string parameter Enlist=false to disable automatic transaction enlistment and create a custom connection provider like this:
This code is part of PainlessDAL framework available at http://code.google.com/p/painlessdal/ .

/// 

/// Manages database connections and transactions
/// 
public class DbContext : IDisposable, IEnlistmentNotification
{
 private string _connectionStringName = null;

 public IDbConnection Connection
 {
  get
  {
   return (IDbConnection)GetContextData("DbContextCONNECTION" + this._connectionStringName);
  }
  private set
  {
   if (value == null)
    ClearContextData("DbContextCONNECTION" + this._connectionStringName);
   else
    SetContextData("DbContextCONNECTION" + this._connectionStringName, value);
  }
 }
 private IDbTransaction DbTransaction
 {
  get
  {
   return (IDbTransaction)GetContextData("DbContextTRANSACTION" + this._connectionStringName);
  }
  set
  {
   if (value == null)
    ClearContextData("DbContextTRANSACTION" + this._connectionStringName);
   else
    SetContextData("DbContextTRANSACTION" + this._connectionStringName, value);
  }
 }
 private int UsageCounter
 {
  get
  {
   return (int)(GetContextData("DbContextUSAGECOUNTER" + this._connectionStringName) ?? 0);
  }
  set
  {
   Debug.Print(this._connectionStringName + " usage: " + value.ToString());
   if (value == 0)
    ClearContextData("DbContextUSAGECOUNTER" + this._connectionStringName);
   else
    SetContextData("DbContextUSAGECOUNTER" + this._connectionStringName, value);
  }
 }
 public DbContext(string connectionStringName)
 {
  this._connectionStringName = connectionStringName;
  this.UsageCounter++;
  if (this.Connection == null)
  {
   this.Connection = DbHelper.GetConnection(connectionStringName, true);
  }
  if (Transaction.Current != null && this.DbTransaction == null)
  {
   Transaction.Current.EnlistVolatile(this, EnlistmentOptions.None);
   System.Transactions.IsolationLevel tIsolation = Transaction.Current.IsolationLevel;
   System.Data.IsolationLevel dbIsolation = (System.Data.IsolationLevel)Enum.Parse(typeof(System.Data.IsolationLevel), tIsolation.ToString());
   this.DbTransaction = this.Connection.BeginTransaction(dbIsolation);
  }
 }
 ~DbContext()
 {
  Dispose();
 }
 private object GetContextData(string key)
 {
  if (HttpContext.Current != null)
   return HttpContext.Current.Items[key];
  else
   return CallContext.GetData(key);
 }
 private void SetContextData(string key, object data)
 {
  if (HttpContext.Current != null)
   HttpContext.Current.Items[key] = data;
  else
   CallContext.SetData(key, data);
 }
 private void ClearContextData(string key)
 {
  if (HttpContext.Current != null)
   HttpContext.Current.Items.Remove(key);
  else
   CallContext.FreeNamedDataSlot(key);
 }
 public void Dispose()
 {
  GC.SuppressFinalize(this);
  this.UsageCounter--;
  CloseConnection();
 }
 private void CloseConnection()
 {
  if (this.UsageCounter == 0 && this.DbTransaction == null)
  {
   if (this.Connection != null)
   {
    this.Connection.Dispose();
    this.Connection = null;
   }
  }
 }

 #region IEnlistmentNotification implementation
 public void Commit(Enlistment enlistment)
 {
  Debug.Print("Commit");
  this.DbTransaction.Commit();
  this.DbTransaction.Dispose();
  this.DbTransaction = null;
  CloseConnection();
  enlistment.Done();
 }

 public void InDoubt(Enlistment enlistment)
 {
  throw new NotImplementedException();
 }

 public void Prepare(PreparingEnlistment preparingEnlistment)
 {
  Debug.Print("Prepare");
  preparingEnlistment.Prepared();
 }

 public void Rollback(Enlistment enlistment)
 {
  Debug.Print("Rollback");
  this.DbTransaction.Rollback();
  this.DbTransaction.Dispose();
  this.DbTransaction = null;
  CloseConnection();
  enlistment.Done();
 }
 #endregion
}