Исправление ошибки, когда не менялось видимость ResultViewer'a. Добавлена возможность запустить новое задание, если в одном из полей изменилось название.

fileFinder/MainForm.cs

@@ -16,14 +16,13 @@ namespace fileFinder
     public partial class MainForm : Form
     {
         HintModel hints = new HintModel();
-        TaskController mainController;
+        TaskController mainController = new TaskController();
         SearchQueryModel searchQueryModel;
         System.Timers.Timer updateInfoTimer = new System.Timers.Timer(1000);
 
         public MainForm()
         {
             InitializeComponent();
-            mainController = new TaskController();
             this.updateInfoTimer.Elapsed += refreshInfoByTimer;
             this.updateInfoTimer.AutoReset = true;
             this.updateInfoTimer.Enabled = true;
@@ -39,6 +38,7 @@ namespace fileFinder
             queryTextBox.Text = sets.fileNameQuery;
             searchQueryModel = mainController.updateSearchQueryModel(sets.fileUrl,
                 sets.fileInnerQuery, sets.fileNameQuery);
+            mainController.isTaskChanged = false;
         }
 
         private void fillImagesToResultViewer()
@@ -94,26 +94,30 @@ namespace fileFinder
 
             if (mainController.isStopped || mainController.isTaskChanged)
             {
+                mainController.stopTask();
+                mainController = new TaskController();
                 searchQueryModel = mainController.updateSearchQueryModel(curDirTextBox.Text,
                     queryTextBox.Text, innerQueryTextBox.Text);
                 handleSearchBtn.Text = "Pause Task";
-                waitOrPauseLabel.Visible = true;
-                resultViewer.Enabled = false;
                 mainController.beginTask();
-                TreeNode tN = await Task.Run(() => mainController.buildResultTree(searchQueryModel, progress));
-                updateResultViewer(tN);
                 changeVisibilityResultViewer();
-                handleSearchBtn.Text = "Start Task";
+                TreeNode tN = await Task.Run(() => mainController.buildResultTree(searchQueryModel, progress));
+                if (tN != null)
+                {
+                    updateResultViewer(tN);
+                    changeVisibilityResultViewer();
+                    handleSearchBtn.Text = "Start Task";
+                }                   
             } else if (mainController.isPaused)
             {
                 handleSearchBtn.Text = "Pause Task";
-                changeVisibilityResultViewer();
                 mainController.resumeTask();
+                changeVisibilityResultViewer();
             } else
             {
                 handleSearchBtn.Text = "Resume Task";
-                changeVisibilityResultViewer();
                 mainController.pauseTask();
+                changeVisibilityResultViewer();
             }
         }
 
@@ -170,17 +174,26 @@ namespace fileFinder
 
         private void curDirTextBox_TextChanged(object sender, EventArgs e)
         {
-            mainController.isTaskChanged = true;
+            changeTaskBtnStatus();
         }
 
         private void queryTextBox_TextChanged(object sender, EventArgs e)
         {
-            mainController.isTaskChanged = true;
+            changeTaskBtnStatus();
         }
 
         private void innerQueryTextBox_TextChanged(object sender, EventArgs e)
         {
-            mainController.isTaskChanged = true;
+            changeTaskBtnStatus();
+        }
+
+        private void changeTaskBtnStatus()
+        {
+            if (!mainController.isTaskChanged)
+            {
+                mainController.isTaskChanged = true;
+                handleSearchBtn.Text = "Start New Task";
+            }
         }
     }
 }

fileFinder/TaskController.cs

@@ -77,6 +77,8 @@ namespace fileFinder
             int counter = 0;
             foreach (string item in foundFiles)
             {
+                if (controller.isStopped)
+                    return null;
                 while (controller.isPaused)
                 {
                     Thread.Sleep(100);