conver VB function to c#

Hughesie78 · April 24th, 2008, 07:08 AM

i have a VB function that i want to convert to c#, relatiely new to C# at the mo, any ideas?
Function FilterForImages(images() as FileInfo) as FileInfo()

Dim newImages as New ArrayList(images.Length)

Dim i as Integer

For i = 0 to images.Length - 1

If Path.GetExtension(images(i).Name.ToLower()) = ".jpg" OrElse _

Path.GetExtension(images(i).Name.ToLower()) = ".jpeg" OrElse _

Path.GetExtension(images(i).Name.ToLower()) = ".png" OrElse _

Path.GetExtension(images(i).Name.ToLower()) = ".bmp" OrElse _

Path.GetExtension(images(i).Name.ToLower()) = ".JPG" OrElse _

Path.GetExtension(images(i).Name.ToLower()) = ".gif" Then

newImages.Add(images(i))

End If

Next

Return CType(newImages.ToArray(GetType(FileInfo)), FileInfo())

End Function

samjudson · April 24th, 2008, 07:25 AM

OK, well first off this isn't a terrible efficient way to do it in VB.Net, especially the line that says ".JPG" since you've just converted the format to lower case so that will never be true.

I'd recommend using regular expressions as well.

Code:

Function FilterForImages(images() as FileInfo) as FileInfo()

Dim newImages as New ArrayList(images.Length)
Dim r As New Regex("^[.](jpg|jpeg|png|bmp|gif)$", RegexOptions.Compiled Or RegexOptions.IgnoreCase)
For i = 0 To image.Length - 1
  If r.IsMatch(Path.GetExtension(images(i).Name)) Then
    newImages.Add(images(i))
  End If
Next

Return CType(newImages.ToArray(GetType(FileInfo)), FileInfo())

End Function

or in C#

Code:

public FileInfo[] FilterForImages(FileInfo[] images)
{
ArrayList newImages = new ArrayList(images.Length);

Regex r = new Regex("^[.](jpg|jpeg|png|bmp|gif)$", RegexOptions.Compiled || RegexOptions.IgnoreCase);
foreach(FileInfo image in images)
{
   if( r.IsMatch(Path.GetExtension(image.Name)) )
   {
     newImages.Add(image); 
   }

   return (FileInfo[])newImages.ToArray(typeof(FileInfo));
}

If you are using .Net 2.0 or higher then you can simplify this even more by using generics, so your newImages array becomes:

Code:

VB.Net
Dim newImages As New List(Of FileInfo)

C#
List<FileInfo> newImages = new List<FileInfo>();

And the last line then becomes

Code:

VB.Net
Return newImages.ToArray()

C#
return newImages.ToArray();

/- Sam Judson : Wrox Technical Editor -/

Hughesie78 · April 24th, 2008, 09:10 AM

I am getting this error now when i compile:
'Gallery.FilterForImages(System.IO.FileInfo[])': not all code paths return a value

my code is:
    public FileInfo[] FilterForImages(FileInfo[] images)
    {
        try
        {

            ArrayList newImages = new ArrayList(images.Length);
            Regex r = new Regex("^[.](jpg|jpeg|png|bmp|gif)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

            foreach (FileInfo image in images)
            {
                if (r.IsMatch(Path.GetExtension(image.Name)))
                {
                    newImages.Add(image);
                }

                {
                    return (FileInfo[])newImages.ToArray(typeof(FileInfo));
                }
            }

        }
        catch (Exception e)
        { e.Message.ToString(); }
    }

samjudson · April 24th, 2008, 09:28 AM

firstly - your 'return' statement should be outside of the foreach loop - and it doesn't need the { } before and after. The way you currently have it it would return after checking only 1 fileinfo. Also, if there where no fileinfo's passed in it would never return.

Code:

foreach()
{
   if()
   {
   }
}

// return goes here
return ...

Secondly as I mentioned above if an empty array was passed in it would never return (this is what the error is saying).

Also, if you catch an error you a) should do something with the error and b) you still have to either return from the function or throw another exception.

If you don't know why you are catching the exception then I'd recommend NOT catching an exception.

Code:

try
{
 ... do stuff
}
catch(Exception ex)
{
  // what to do with the exception?

  // output to console? Is that helpful?
  Console.WriteLine(ex.ToString());

  // rethrow? In which case why catch it in the first place?
  throw ex;
}

If you don't throw an exception then you need to return something, e.g. return null; or return new FileInfo[0];

/- Sam Judson : Wrox Technical Editor -/

Hughesie78 · April 24th, 2008, 11:04 AM

cool.thanks that worked.

Hughesie78 · April 24th, 2008, 11:05 AM

ok.. i now need to convert this VB to C#:
Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        ''Get list of images
        Dim dirInfo As New DirectoryInfo(Server.MapPath(""))
        ' Dim dirInfo As New DirectoryInfo(Request.PhysicalApplicationPath + "\\Images")

        Dim images() As FileInfo = FilterForImages(dirInfo.GetFiles())

        'Determine the current image to show
        Dim imgIndex As Integer = 0
        If Not Request.QueryString("N") Is Nothing AndAlso IsNumeric(Request.QueryString("N")) Then
            imgIndex = CInt(Request.QueryString("N"))
        End If

        currentImgTitle.Text = "" & _
Right(Path.GetFileNameWithoutExtension(images(imgI ndex).Name),
Len(Path.GetFileNameWithoutExtension(images(imgInd ex).Name)) - 4) '& _

        '" (" & imgIndex + 1 & " of " & images.Length & ")"
        currentImg.ImageUrl = Path.GetFileName(images(imgIndex).Name)

        If imgIndex > 0 Then
            lnkPrev.NavigateUrl = "Default.aspx?N=" & imgIndex - 1
        End If

        If imgIndex < images.Length - 1 Then
            lnkNext.NavigateUrl = "Default.aspx?N=" & imgIndex + 1
        End If

        dlIndex.DataSource = images
        dlIndex.DataBind()
    End Sub

Dave Doknjas · April 24th, 2008, 07:10 PM

(Instant C#)

You'll have to replace the call to IsNumeric - there's no direct .NET equivalent:

public void Page_Load(object sender, EventArgs e)
{
        //'Get list of images
        DirectoryInfo dirInfo = new DirectoryInfo(Server.MapPath(""));
        // Dim dirInfo As New DirectoryInfo(Request.PhysicalApplicationPath + "\\Images")

        FileInfo[] images = FilterForImages(dirInfo.GetFiles());

        //Determine the current image to show
        int imgIndex = 0;
        if (Request.QueryString["N"] != null && Microsoft.VisualBasic.Information.IsNumeric(Reques t.QueryString["N"]))
        {
            imgIndex = System.Convert.ToInt32(Request.QueryString["N"]);
        }

        currentImgTitle.Text = "" + Path.GetFileNameWithoutExtension(images[imgIndex].Name).Substring(Path.GetFileNameWithoutExtension( images[imgIndex].Name).Length - (Path.GetFileNameWithoutExtension(images[imgIndex].Name).Length - 4)); //&
        //" (" & imgIndex + 1 & " of " & images.Length & ")"
        currentImg.ImageUrl = Path.GetFileName(images[imgIndex].Name);

        if (imgIndex > 0)
        {
            lnkPrev.NavigateUrl = "Default.aspx?N=" + imgIndex - 1;
        }

        if (imgIndex < images.Length - 1)
        {
            lnkNext.NavigateUrl = "Default.aspx?N=" + (imgIndex + 1);
        }

        dlIndex.DataSource = images;
        dlIndex.DataBind();
    }

robzyc · April 25th, 2008, 02:29 AM

I have a feeling this is going to continue until the entire app is converted :)

Might I suggest getting a "Teach Yourself .NET" Book that is language neutral, most of these books will have both VB and C# code so you can see the code side-by-side, once you have the basic constructs down, conversion becomes a lot easier. You begin to see more the .NET code rather than the VB/C#..

Obviously there are some C# goodies that we have (special constructs to do things slightly "better"/easier - such as "using") but we can assist with those if you need it :)

Rob
http://robzyc.spaces.live.com

Hughesie78 · April 25th, 2008, 03:54 AM

:):D
thanbks for that, ya got it in one yes im trying to convert an aspx page from VB to C#, here is the very last piece, no more after this i prmise.
Sub dlIndex_ItemDataBound(ByVal sender As Object, ByVal e As DataListItemEventArgs)

If e.Item.ItemType = ListItemType.Item OrElse e.Item.ItemType = ListItemType.AlternatingItem Then

Dim hl As HyperLink = CType(e.Item.FindControl("lnkPic"), HyperLink)

hl.Text = Right(Path.GetFileNameWithoutExtension(DataBinder. Eval(e.Item.DataItem, "Name").ToString()), Len(Path.GetFileNameWithoutExtension(DataBinder.Ev al(e.Item.DataItem, "Name").ToString())) - 4) '& _

hl.NavigateUrl = "Default.aspx?N=" & e.Item.ItemIndex

End If

End Sub

Hughesie78 · April 25th, 2008, 03:55 AM

Robzyc, thanks for the book suggestion.