If you are happy with it, fine

I had something slightly different in mind

A class that loads the image the first time it is needed
I don't know how and where all your pieces fit together

I've put it all in one class. I like that better.. I don't like oImageData to be public

The class below is thread safe

	static  class TestImage
	{
		internal static void Go()
		{
			string imageName = "123.jpg";
			ImageData imageData;

			if (ImageLibrary.TryGetImage(imageName, out imageData))
				Console.WriteLine("Found It");
			else
				Console.WriteLine("Did not find it");
		}
	}

	class ImageData
	{
		internal int Width { get; private set; }
		internal int Height { get; private set; }

		internal ImageData(int width, int height)
		{
			Width = width;
			Height = height;
		}
	}

	static class ImageLibrary
	{
		static Dictionary<string, ImageData> Library = new Dictionary<string, ImageData>();
		static HashSet<string> FailedLoads = new HashSet<string>();
		static object ImageAddLocker = new object();

		static ImageLibrary()
		{
			// if you want to preload images, do it here
			// otherwise take out this static constructor
		}

		internal static bool TryGetImage(string imageName, out ImageData imageData)
		{
			string name = imageName.ToUpper();

			if (Library.TryGetValue(name, out imageData))
				return true;

			if (FailedLoads.Contains(name))
				return false;

			if (!TryFindImage(name, out imageData))
			{
				FailedLoads.Add(name);
				return false;
			}

			AddImage(name, imageData);

			return true;
		}

		static bool TryFindImage(string name, out ImageData imageData)
		{
			string imageFullPath = Path.Combine(@"d:\tmp", name);
			//string imageFullPath = Path.Combine(oApp.cGraphicFat, name);

			if (File.Exists(imageFullPath))
			{
				Bitmap bitmap = new System.Drawing.Bitmap(imageFullPath);

				imageData = new ImageData(bitmap.Width, bitmap.Height);
				return true;
			}

			imageData = default(ImageData);
			return false;
		}
		static void AddImage(string name, ImageData imageData)
		{
			lock (ImageAddLocker)
			{
				if (!Library.ContainsKey(name))
					Library.Add(name, imageData);
			}
		}
	}

>Ok, here is a revised version. This works. I had to make reference to a higher object declared at the application level and work with it along the way.
>
>This is the application class declaration:
>
>

>    ' Images in memory
>    Public oImageData As Dictionary(Of String, ImageData) = New Dictionary(Of String, ImageData)
>

>
>This is the application class ImageData:
>
>

>' ImageData class
>Public Class ImageData
>    Private cExtension As String = ""
>    Private nHeight As Integer = 0
>    Private nWidth As Integer = 0
>
>    Friend Property Extension() As String
>        Get
>            Return cExtension
>        End Get
>        Private Set(tcValue As String)
>            cExtension = tcValue
>        End Set
>    End Property
>
>    Friend Property Height() As Integer
>        Get
>            Return nHeight
>        End Get
>        Private Set(tnValue As Integer)
>            nHeight = tnValue
>        End Set
>    End Property
>
>    Friend Property Width() As Integer
>        Get
>            Return nWidth
>        End Get
>        Private Set(tnValue As Integer)
>            nWidth = tnValue
>        End Set
>    End Property
>
>    Friend Sub New(tnWidth As Integer, tnHeight As Integer, tcExtension As String)
>        Width = tnWidth
>        Height = tnHeight
>        Extension = tcExtension
>    End Sub
>
>End Class
>

>
>This is the initialization part:
>
>

>        ' If this is the Web site
>        If oApp.nApplicationMode = 3 Then
>
>            ' If we have some images in memory
>            If oApp.oAdmin.oRow("Image").length > 0 Then
>
>                ' Load the application into the string builder
>                loStringBuilderFile.LoadString(oApp.oAdmin.oRow("Image"))
>
>                ' For each image
>                For lnCounter = 1 To loStringBuilderFile.nLine
>
>                    ' Get the line
>                    If Not loStringBuilderFile.MLine(lnCounter) Then
>                        Return False
>                    End If
>
>                    lcImage = loStringBuilderFile.cLine
>
>                    ' If the file exists
>                    If oApp.FileExist(oApp.cGraphicFat + lcImage) Then
>
>                        ' Get the image details making it OK to reender the HTML without flickering
>                        loImage = New System.Drawing.Bitmap(oApp.cGraphicFat + lcImage)
>                        lnWidth = loImage.Width
>                        lnHeight = loImage.Height
>
>                        ' Initializaiton
>                        lcName = Trim(lcImage)
>                        lnLocation = oApp.At(".", lcName)
>                        lcExtension = ""
>
>                        ' If we have found it
>                        If lnLocation > 0 Then
>
>                            ' If this is not the last character
>                            If lnLocation < lcName.Length Then
>                                lcExtension = Mid(lcName, lnLocation + 1)
>                            End If
>
>                        End If
>
>                        oApp.oImageData.Add(UCase(lcImage), New ImageData(lnWidth, lnHeight, lcExtension))
>                    Else
>                        AddError(oApp.cGraphicFat + lcImage + " does not exist.")
>                    End If
>
>                Next
>
>            End If
>
>        End If
>

>
>This is the query part:
>
>

>    ' Return True or False if an image is loaded in memory
>    ' expC1 Name
>    Public Function IsImageInMemory(ByVal tcName As String) As Boolean
>        Dim lcName As String = ""
>        Dim llFound As Boolean = False
>        Dim loImageData As ImageData = Nothing
>
>        ' Initialization
>        lcName = UCase(Trim(tcName))
>
>        ' If the image is found in the dictionary
>        If oProcess.oApp.oImageData.TryGetValue(lcName, loImageData) Then
>            llFound = True
>
>            ' Initialization
>            nWidth = loImageData.Width
>            nHeight = loImageData.Height
>
>        End If
>
>        Return llFound
>    End Function
>