Shell32 Interop DLL Generation

As far as I’m aware you’ve got two choices when you want to call non .NET assemblies, DllImport or Interop.

For DllImport you’ll want to consult pinvoke.net.

But that DllImport syntax isn’t for everyone, some like to pretend we are working with .NET assemblies and want to use an Interop DLL, but how?

First you need to generate one using Tlbimp.exe (Type Library Importer)
For example
c:\Windows\System32>tlbimp shell32.dll /out:me.dll
Microsoft (R) .NET Framework Type Library to Assembly Converter 3.5.30729.1
Copyright (C) Microsoft Corporation. All rights reserved.
Type library imported to c:\Windows\System32\me.dll

Now just include the me.dll in your project (as a normal .NET assembly reference), stick a “using Shell32 = me;” / “Import Shell32 = me” in your source code and voila, Shell32.Folder etc is at your disposal.

Note: retrospectively thinking, don’t generate the dll into System32, you’re just asking for trouble.

Unit Test Projects and NUnit compatibility

I often need to write Unit Tests and have them accessible from NUnit as well as the Visual Studio Test View (etc), so I thought I’d write myself a walkthrough of the common things I have to do.

Firstly, whichever language I’m using, Visual Studio is normally configured to create the wrong one, so let’s say I’ve got my C# hat on and I create a test project:

Darn it, it’s created a VB.NET one, so I delete it and search for the setting or way I create a C# one. This can be located under Tools -> Options -> Test Tools -> Test Project, then choose your preference from the “Default test project language” dropdown, like so:

You will also notice you can choose what (if any) template test classes are created for you. 99% of the time I use Unit Test and that is it.
So you go back in and create the project again and it’s created a C# one, it automatically adds a reference to the Visual Studio Test classes, great:

Add a reference to NUnit, so you have:

Now let’s look at the Unit Test class, I’ve stripped it down to the bare bones:

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace TestProject1
{
    [TestClass]
    public class UnitTest1
    {
        [TestMethod]
        public void TestMethod1()
        {
        }
    }
}

Since we don’t want the Visual Studio and the NUnit classes to conflict my approach is to take out the Visual Studio using statement like so:

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;

namespace TestProject1
{
    [Microsoft.VisualStudio.TestTools.UnitTesting.TestClass]
    public class UnitTest1
    {
        [Microsoft.VisualStudio.TestTools.UnitTesting.TestMethod]
        public void TestMethod1()
        {
        }
    }
}

Now this will still work as before, but we can add NUnit in now too, like so:

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using NUnit.Framework;

namespace TestProject1
{
    [Microsoft.VisualStudio.TestTools.UnitTesting.TestClass]
    [TestFixture]
    public class UnitTest1
    {
        [Microsoft.VisualStudio.TestTools.UnitTesting.TestMethod]
        [Test]
        public void TestMethod1()
        {
        }
    }
}

And proof of the pudding, Visual Studio:

NUnit:

This also reminds me, while I’m on the subject, to be able to open a Visual Studio project from within NUnit there is a setting you need to change, go to Tools -> Settings -> IDE Support -> Visual Studio and then tick the “Enable Visual Studio Support” checkbox, like so:

Null coalesce operator

Null coalesce operators:

C# – ??

int? myVar = null;
System.Console.Write(myVar ?? 0);

VB.NET – If ()

Dim myVar As Nullable(Of int) = Nothing
System.Console.Write(If(myVar, 0))

Ternary Operators

Ternary Operators:

VB.NET – IIf ()

IIf (predicate, valueiftrue, valueiffalse)

C# – ?:

predicate ? valueiftrue : valueiffalse

LINQ to SQL Transactions

The thing about Transactions in LINQ is that they are rubbish.
It’s all designed around submitting changes to a transaction, great, but if you rollback the transaction those changes can not be submitted a second time, you’d have to manually undo the changes or recreate the DataContext and apply the changes once more.

Below are some examples I put together whilst trying out LINQ to SQL, as they are copied from a Wiki I used to have, please let me know if you spot any errors.

Here’s an example of this with an insert.

VB.NET

Dim testerString As String = "HELLO"
Dim meeee As LINQtoSQLDataClassesDataContext = Nothing

Try
    ' New DataContext
    meeee = New LINQtoSQLDataClassesDataContext() With {.Log = Console.Out}

    ' Open connection
    meeee.Connection.Open()

    ' New transaction
    meeee.Transaction = meeee.Connection.BeginTransaction()

    ' Insert command
    meeee.TableAs.InsertOnSubmit(New TableA() With {.Name = testerString, .Region = "East"})

    ' Submit changes (to the transaction)
    meeee.SubmitChanges()

    ' Rollback
    meeee.Transaction.Rollback()

    ' This would fail on submit because the in memory would have a duplicate - which is annoying but kind of makes sense

    'meeee.Transaction = meeee.Connection.BeginTransaction()
    'meeee.TableAs.InsertOnSubmit(New TableA() With {.Name = testerString, .Region = "West"})
    'meeee.SubmitChanges()
    'meeee.Transaction.Commit()

    ' This would have no effect - changes already submitted, so there are none

    'meeee.Transaction = meeee.Connection.BeginTransaction()
    'meeee.SubmitChanges()
    'meeee.Transaction.Commit()

    ' This would have no effect - once submitted there doesn't appear to be any way back

    'meeee.Transaction = meeee.Connection.BeginTransaction()
    'meeee.Refresh(--of any kind--)
    'meeee.SubmitChanges()
    'meeee.Transaction.Commit()
Finally
    If (Not meeee Is Nothing) Then
        If (Not meeee.Connection Is Nothing) Then
            meeee.Connection.Close()
        End If

        meeee.Dispose()
    End If
End Try

C#

String testerString = "HELLO";
LINQtoSQLDataClassesDataContext meeee = null;

try
{
    // New DataContext
    meeee = new LINQtoSQLDataClassesDataContext() { Log = Console.Out };

    // Open connection
    meeee.Connection.Open();

    // New transaction
    meeee.Transaction = meeee.Connection.BeginTransaction();

    // Insert command
    meeee.TableAs.InsertOnSubmit(new TableA() { Name = testerString, Region = "East" });

    // Submit changes (to the transaction)
    meeee.SubmitChanges();

    // Rollback
    meeee.Transaction.Rollback();

    // This would fail on submit because the in memory would have a duplicate - which is annoying but kind of makes sense

    //meeee.Transaction = meeee.Connection.BeginTransaction();
    //meeee.TableAs.InsertOnSubmit(new TableA() { Name = testerString, Region = "West" });
    //meeee.SubmitChanges();
    //meeee.Transaction.Commit();

    // This would have no effect - changes already submitted, so there are none

    //meeee.Transaction = meeee.Connection.BeginTransaction();
    //meeee.SubmitChanges();
    //meeee.Transaction.Commit();

    // This would have no effect - once submitted there doesn't appear to be any way back

    //meeee.Transaction = meeee.Connection.BeginTransaction();
    //meeee.Refresh(--of any kind--);
    //meeee.SubmitChanges();
    //meeee.Transaction.Commit();
}
finally
{
    if (null != meeee)
    {
        if (null != meeee.Connection)
        {
            meeee.Connection.Close();
        }

        meeee.Dispose();
    }
}

This next part is the retry i.e. ditch it and redo

VB.NET

' Start a clean DataContext if you want to retry / redo the updates

Dim meee2 As LINQtoSQLDataClassesDataContext = Nothing

Try
    meee2 = New LINQtoSQLDataClassesDataContext() With {.Log = Console.Out}
    meee2.Connection.Open()
    meee2.Transaction = meee2.Connection.BeginTransaction()
    meee2.TableAs.InsertOnSubmit(New TableA() With {.Name = testerString, .Region = "South"})
    meee2.SubmitChanges()
    meee2.Transaction.Commit()
Finally
    If (Not meee2 Is Nothing) Then
        If (Not meee2.Connection Is Nothing) Then
            meee2.Connection.Close()
        End If

        meee2.Dispose()
    End If
End Try

C#

// Start a clean DataContext if you want to retry  redo the updates

LINQtoSQLDataClassesDataContext meee2 = null;

try
{
    meee2 = new LINQtoSQLDataClassesDataContext() { Log = Console.Out };
    meee2.Connection.Open();
    meee2.Transaction = meee2.Connection.BeginTransaction();
    meee2.TableAs.InsertOnSubmit(new TableA() { Name = testerString, Region = "South" });
    meee2.SubmitChanges();
    meee2.Transaction.Commit();
}
finally
{
    if (null != meee2)
    {
        if (null != meee2.Connection)
        {
            meee2.Connection.Close();
        }

        meee2.Dispose();
    }
}

Now is an example of a delete:

VB.NET

' Delete it

Dim meee3 As LINQtoSQLDataClassesDataContext = Nothing

Try
    meee3 = New LINQtoSQLDataClassesDataContext() With {.Log = Console.Out}
    meee3.Connection.Open()
    meee3.Transaction = meee3.Connection.BeginTransaction()
    meee3.TableAs.DeleteOnSubmit( _
                meee3.TableAs.Where(Function(x) x.Name = testerString).Select(Function(x) x).FirstOrDefault())
    meee3.SubmitChanges()
    meee3.Transaction.Commit()
Finally
    If (Not meee3 Is Nothing) Then
        If (Not meee3.Connection Is Nothing) Then
            meee3.Connection.Close()
        End If

        meee3.Dispose()
    End If
End Try

C#

// Delete it

LINQtoSQLDataClassesDataContext meee3 = null;

try
{
    meee3 = new LINQtoSQLDataClassesDataContext() { Log = Console.Out };
    meee3.Connection.Open();
    meee3.Transaction = meee3.Connection.BeginTransaction();
    meee3.TableAs.DeleteOnSubmit(
        meee3.TableAs.Where(x => x.Name == testerString).Select(x => x).FirstOrDefault());
    meee3.SubmitChanges();
    meee3.Transaction.Commit();
}
finally
{
    if (null != meee3)
    {
        if (null != meee3.Connection)
        {
            meee3.Connection.Close();
        }

        meee3.Dispose();
    }
}

LINQ Basic DataSource binding

This is a quick example of LINQ and binding to a DataGridView control (via DataSource) the property name is used as the column header (Column[idx].HeaderText) this can be change via the following attribute:
System.ComponentModel.DisplayName(“Column header name here”)

The following example uses a LINQ query on a string collection to demonstrate this:

C#

var objCollection = from objs in fileStringCollection
                    select new WrapperForStrings
                    {StringProperty = objs};
this.DataGridView2.DataSource = objCollection.ToList();
this.DataGridView2.AutoResizeColumns();
...
public class WrapperForStrings
{
    private String stringValue;

    [System.ComponentModel.DisplayName("Column header name here C#")]
    public String StringProperty
    {
        get
        {
            return stringValue;
        }
        set
        {
            stringValue = value;
        }
    }
}

VB.NET

Dim objCollection = From objs In fileStringCollection _
                    Select New WrapperForStrings _
                    With {.StringProperty = objs}
Me.DataGridView2.DataSource = objCollection.ToList()
Me.DataGridView2.AutoResizeColumns()
...
Public Class WrapperForStrings
    Private stringValue As String

    <System.ComponentModel.DisplayName("Column header name here VB")> _
    Public Property StringProperty() As String
        Get
            Return stringValue
        End Get
        Set(ByVal value As String)
            stringValue = value
        End Set
    End Property
End Class

LINQ Distinct / Group By

LINQ offers up a nice way to group items and you can even reference the grouping values called keys.

Here’s an example of grouping a collection of Strings based on their length:

VB.NET

' VB requires the = Group part, but Group str By doesn't need the str part.
Dim myList = From str In fileStringCollection _
             Order By str.Length _
             Group By str.Length Into filGrouping = Group

C#

// Of course C# can't have the = Group part, requires the group str by to have the str part and requires the select
var myList = from str in fileStringCollection
             orderby str.Length
             group str by str.Length into filGrouping
             select new { filGrouping = filGrouping, Length = filGrouping.Key };

Here filGrouping behaves like a variable within the scope of the expression, we can look at the distinct values for the Length of the Strings by using the filGrouping.Key. Here we are returning the grouping, if you enumerate the grouping you get each of the Strings for that String Length.

For more on DISTINCT / GROUP BY see my more recent post (from a database point of view) SQL Server / Oracle: DISTINCT or GROUP BY

LINQ Basic Selects

Whether a select is required or not

VB.NET

' Notice no select is required
Dim fileStringCollection = From anythingGoesHere _
                           In My.Computer.FileSystem.GetFiles("C:\")

C#

// Select is required
var fileStringCollection = from anythingGoesHere
                           in Directory.GetFiles(@"C:\")
                           select anythingGoesHere;

Selecting into an object / properties

VB.NET

Dim objCollection = From objs _
                    In fileStringCollection _
                    Select New WrapperForStrings _
                      With {.StringProperty = objs}

C#

var objCollection = from objs
                    in fileStringCollection
                    select new WrapperForStrings
                      {StringProperty = objs};

Returning multiple columns (via an instance of an anonymous class) in a select

VB.NET

' VB can just use a plain syntax as follows
Dim myInfoCollection = From file In filesInfoCollection _
                       Select file.Name, file.CreationTime

C#

// In C# you must explicitly create a new (anonymous) object and explicitly define the properties and values
var myInfoCollection = from file in filesInfoCollection
                       select new { CSName = file.Name,
                         CSCreationTime = file.CreationTime };

Edit: For an example of WrapperForStrings see this post