Remember decompiled nodes before starting decompilation, this fixes problems with changing tabs while a decompilation is in progress.

ILSpy/TextView/DecompilerTextView.cs

@@ -152,7 +152,7 @@ namespace ICSharpCode.ILSpy.TextView
 		{
 			if (this.DataContext is PaneModel model)
 			{
-				model.Title = currentTitle ?? ILSpy.Properties.Resources.NewTab;
+				model.Title = currentTitle ?? ILSpy.Properties.Resources.Decompiling;
 			}
 		}
 
@@ -665,8 +665,8 @@ namespace ICSharpCode.ILSpy.TextView
 				textOutput.Title = string.Join(", ", nodes.Select(n => n.Text));
 			}
 
-			ShowOutput(textOutput, highlighting);
 			decompiledNodes = nodes;
+			ShowOutput(textOutput, highlighting);
 		}
 
 		/// <summary>
@@ -815,12 +815,12 @@ namespace ICSharpCode.ILSpy.TextView
 			return RunWithCancellation(
 				delegate (CancellationToken ct) { // creation of the background task
 					context.Options.CancellationToken = ct;
+					decompiledNodes = context.TreeNodes;
 					return DecompileAsync(context, outputLengthLimit);
 				})
 			.Then(
 				delegate (AvalonEditTextOutput textOutput) { // handling the result
 					ShowOutput(textOutput, context.Language.SyntaxHighlighting, context.Options.TextViewState);
-					decompiledNodes = context.TreeNodes;
 				})
 			.Catch<Exception>(exception => {
 				textEditor.SyntaxHighlighting = null;
@@ -835,7 +835,6 @@ namespace ICSharpCode.ILSpy.TextView
 					output.WriteLine(exception.ToString());
 				}
 				ShowOutput(output);
-				decompiledNodes = context.TreeNodes;
 			});
 		}
 

ILSpy/ViewModels/TabPageModel.cs

@@ -96,6 +96,7 @@ namespace ICSharpCode.ILSpy.ViewModels
 				textView = new DecompilerTextView();
 				tabPage.Content = textView;
 			}
+			tabPage.Title = Properties.Resources.Decompiling;
 			return action(textView);
 		}
 
@@ -106,6 +107,7 @@ namespace ICSharpCode.ILSpy.ViewModels
 				textView = new DecompilerTextView();
 				tabPage.Content = textView;
 			}
+			tabPage.Title = Properties.Resources.Decompiling;
 			return action(textView);
 		}
 
@@ -116,6 +118,7 @@ namespace ICSharpCode.ILSpy.ViewModels
 				textView = new DecompilerTextView();
 				tabPage.Content = textView;
 			}
+			tabPage.Title = Properties.Resources.Decompiling;
 			action(textView);
 		}
 	}