diff --git a/ILSpy.AddIn/Commands/OpenILSpyCommand.cs b/ILSpy.AddIn/Commands/OpenILSpyCommand.cs
index 8e8e48193..6f1261d3c 100644
--- a/ILSpy.AddIn/Commands/OpenILSpyCommand.cs
+++ b/ILSpy.AddIn/Commands/OpenILSpyCommand.cs
@@ -12,18 +12,6 @@ using Mono.Cecil;
 
 namespace ICSharpCode.ILSpy.AddIn.Commands
 {
-	public class ILSpyParameters
-	{
-		public ILSpyParameters(IEnumerable<string> assemblyFileNames, params string[] arguments)
-		{
-			this.AssemblyFileNames = assemblyFileNames;
-			this.Arguments = arguments;
-		}
-
-		public IEnumerable<string> AssemblyFileNames { get; private set; }
-		public string[] Arguments { get; private set; }
-	}
-
 	public class DetectedReference
 	{
 		public DetectedReference(string name, string assemblyFile, bool isProjectReference)
@@ -75,12 +63,8 @@ namespace ICSharpCode.ILSpy.AddIn.Commands
 				}
 			}
 
-			string commandLineArguments = Utils.ArgumentArrayToCommandLine(parameters.AssemblyFileNames.ToArray());
-			if (parameters.Arguments != null) {
-				commandLineArguments = string.Concat(commandLineArguments, " ", Utils.ArgumentArrayToCommandLine(parameters.Arguments));
-			}
-
-			System.Diagnostics.Process.Start(GetILSpyPath(), commandLineArguments);
+			var ilspyExe = new ILSpyInstance(parameters);
+			ilspyExe.Start();
 		}
 
 		protected Dictionary<string, DetectedReference> GetReferences(Microsoft.CodeAnalysis.Project parentProject)
@@ -140,7 +124,7 @@ namespace ICSharpCode.ILSpy.AddIn.Commands
 
 		protected override void OnExecute(object sender, EventArgs e)
 		{
-			System.Diagnostics.Process.Start(GetILSpyPath());
+			new ILSpyInstance().Start();
 		}
 
 		internal static void Register(ILSpyAddInPackage owner)
diff --git a/ILSpy.AddIn/ILSpy.AddIn.csproj b/ILSpy.AddIn/ILSpy.AddIn.csproj
index ee784cab3..01817bbcf 100644
--- a/ILSpy.AddIn/ILSpy.AddIn.csproj
+++ b/ILSpy.AddIn/ILSpy.AddIn.csproj
@@ -74,6 +74,7 @@
     <Compile Include="Commands\OpenProjectOutputCommand.cs" />
     <Compile Include="Commands\OpenReferenceCommand.cs" />
     <Compile Include="Guids.cs" />
+    <Compile Include="ILSpyInstance.cs" />
     <Compile Include="Resources.Designer.cs">
       <AutoGen>True</AutoGen>
       <DesignTime>True</DesignTime>
diff --git a/ILSpy.AddIn/ILSpyInstance.cs b/ILSpy.AddIn/ILSpyInstance.cs
new file mode 100644
index 000000000..fe4ee1abc
--- /dev/null
+++ b/ILSpy.AddIn/ILSpyInstance.cs
@@ -0,0 +1,116 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace ICSharpCode.ILSpy.AddIn
+{
+	class ILSpyParameters
+	{
+		public ILSpyParameters(IEnumerable<string> assemblyFileNames, params string[] arguments)
+		{
+			this.AssemblyFileNames = assemblyFileNames;
+			this.Arguments = arguments;
+		}
+
+		public IEnumerable<string> AssemblyFileNames { get; private set; }
+		public string[] Arguments { get; private set; }
+	}
+
+	class ILSpyInstance
+	{
+		ILSpyParameters parameters;
+
+		public ILSpyInstance()
+		{
+		}
+
+		public ILSpyInstance(ILSpyParameters parameters)
+		{
+			this.parameters = parameters;
+		}
+
+		static string GetILSpyPath()
+		{
+			var basePath = Path.GetDirectoryName(typeof(ILSpyAddInPackage).Assembly.Location);
+			return Path.Combine(basePath, "ILSpy.exe");
+		}
+
+		public void Start()
+		{
+			var commandLineArguments = parameters.AssemblyFileNames?.Concat(parameters.Arguments);
+
+			var process = new Process() {
+				StartInfo = new ProcessStartInfo() {
+					FileName = GetILSpyPath(),
+					UseShellExecute = false
+				}
+			};
+			process.Start();
+
+			if ((commandLineArguments != null) && commandLineArguments.Any()) {
+				// Only need a message to started process if there are any parameters to pass
+				SendMessage(process, "ILSpy:\r\n" + string.Join(Environment.NewLine, commandLineArguments), true);
+			}
+		}
+
+		void SendMessage(Process ilspyProcess, string message, bool activate)
+		{
+			// We wait asynchronously until target window can be found and try to find it multiple times
+			Task.Run(async () => {
+				bool success = false;
+				int remainingAttempts = 20;
+				do {
+					NativeMethods.EnumWindows(
+						(hWnd, lParam) => {
+							uint processId = NativeMethods.GetProcessIdFromWindow(hWnd);
+							//if (processId == ilspyProcess.Id) {
+								Debug.WriteLine("Found {0:x4} for process {1}", hWnd, processId);
+								string windowTitle = NativeMethods.GetWindowText(hWnd, 100);
+								if (windowTitle.StartsWith("ILSpy", StringComparison.Ordinal)) {
+									Debug.WriteLine("Found {0:x4}: {1}", hWnd, windowTitle);
+									IntPtr result = Send(hWnd, message);
+									Debug.WriteLine("WM_COPYDATA result: {0:x8}", result);
+									if (result == (IntPtr)1) {
+										if (activate)
+											NativeMethods.SetForegroundWindow(hWnd);
+										success = true;
+										return false; // stop enumeration
+									}
+								}
+							//}
+							return true; // continue enumeration
+						}, IntPtr.Zero);
+
+					// Wait some time before next attempt
+					await Task.Delay(500);
+					remainingAttempts--;
+				} while (!success && (remainingAttempts > 0));
+			});
+		}
+
+		unsafe static IntPtr Send(IntPtr hWnd, string message)
+		{
+			const uint SMTO_NORMAL = 0;
+
+			CopyDataStruct lParam;
+			lParam.Padding = IntPtr.Zero;
+			lParam.Size = message.Length * 2;
+			fixed (char* buffer = message) {
+				lParam.Buffer = (IntPtr)buffer;
+				IntPtr result;
+				// SendMessage with 3s timeout (e.g. when the target process is stopped in the debugger)
+				if (NativeMethods.SendMessageTimeout(
+					hWnd, NativeMethods.WM_COPYDATA, IntPtr.Zero, ref lParam,
+					SMTO_NORMAL, 3000, out result) != IntPtr.Zero) {
+					return result;
+				} else {
+					return IntPtr.Zero;
+				}
+			}
+		}
+	}
+}
diff --git a/ILSpy/NativeMethods.cs b/ILSpy/NativeMethods.cs
index 1513d66ae..f2eb56989 100644
--- a/ILSpy/NativeMethods.cs
+++ b/ILSpy/NativeMethods.cs
@@ -50,6 +50,20 @@ namespace ICSharpCode.ILSpy
 		[DllImport("user32.dll", CharSet = CharSet.Auto)]
 		[return: MarshalAs(UnmanagedType.Bool)]
 		internal static extern bool SetForegroundWindow(IntPtr hWnd);
+
+		//HANDLE WINAPI GetProcessHandleFromHwnd(
+		//  _In_ HWND hwnd
+		//);
+
+		[DllImport("user32.dll", CharSet = CharSet.Auto)]
+		[return: MarshalAs(UnmanagedType.I4)]
+		internal static extern uint GetWindowThreadProcessId(IntPtr hWnd, [MarshalAs(UnmanagedType.I4)] out uint processId);
+
+		public static uint GetProcessIdFromWindow(IntPtr hWnd)
+		{
+			GetWindowThreadProcessId(hWnd, out uint processId);
+			return processId;
+		}
 	}
 	
 	[return: MarshalAs(UnmanagedType.Bool)]