Fix SaveToDisk default filename suggestion to use the text of the tree node instead. The ToString() implementation returns the tree node path, which always starts with the full path of the loaded assembly. So in my case the suggested file name was always "C" when the assembly was located on the C: drive.

ILSpy/TextView/DecompilerTextView.cs

@@ -1091,7 +1091,7 @@ namespace ICSharpCode.ILSpy.TextView
 			SaveFileDialog dlg = new SaveFileDialog();
 			dlg.DefaultExt = language.FileExtension;
 			dlg.Filter = language.Name + "|*" + language.FileExtension + Properties.Resources.AllFiles;
-			dlg.FileName = WholeProjectDecompiler.CleanUpFileName(treeNodes.First().ToString(), language.FileExtension);
+			dlg.FileName = WholeProjectDecompiler.CleanUpFileName(treeNodes.First().Text.ToString(), language.FileExtension);
 			if (dlg.ShowDialog() == true)
 			{
 				SaveToDisk(new DecompilationContext(language, treeNodes.ToArray(), options), dlg.FileName);