Does SqlCommand.Clone() create a deep copy or shallow copy?

Question

Does SqlCommand.Clone() create a deep copy or shallow copy? Also, is it safe to call Clone() from multiple threads concurrently (create one command that multiple threads can copy, set parameter values, and execute)?

Answer 1

It is not safe to call Clone from multiple threads because the SqlCommand class itself is not a thread safe class. you should lock before cloning..

However you can look at the SqlCommand.Clone() method using programs like Reflector, here is the actual code:

public SqlCommand Clone()
{
    SqlCommand command = new SqlCommand(this);
    Bid.Trace("<sc.SqlCommand.Clone|API> %d#, clone=%d#\n", this.ObjectID, command.ObjectID);
    return command;
}

internal static void Trace(string fmtPrintfW, int a1, int a2)
{
    if (((modFlags & ApiGroup.Trace) != ApiGroup.Off) && (modID != NoData))
    {
        NativeMethods.Trace(modID, UIntPtr.Zero, UIntPtr.Zero, fmtPrintfW, a1, a2);
    }
}

[DllImport("System.Data.dll", EntryPoint="DllBidTraceCW", CallingConvention=CallingConvention.Cdecl, CharSet=CharSet.Unicode)]
internal static extern void Trace(IntPtr hID, UIntPtr src, UIntPtr info, string fmtPrintfW, int a1, int a2);

private SqlCommand(SqlCommand from) : this()
{
    this.CommandText = from.CommandText;
    this.CommandTimeout = from.CommandTimeout;
    this.CommandType = from.CommandType;
    this.Connection = from.Connection;
    this.DesignTimeVisible = from.DesignTimeVisible;
    this.Transaction = from.Transaction;
    this.UpdatedRowSource = from.UpdatedRowSource;
    SqlParameterCollection parameters = this.Parameters;
    foreach (object obj2 in from.Parameters)
    {
        parameters.Add((obj2 is ICloneable) ? (obj2 as ICloneable).Clone() : obj2);
    }
}

You can see that it create a new instance and add to it all properties of the old one, but it does not deep copy all properties "like Connection for instance" and so it a shallow copy.