在 FolderBrowserDialog 返回 "" 时不修改 TextBox 的值

src/Extensions/SystemExtensions.cs

@@ -21,5 +21,7 @@ public static Exception ShowAndLog(this Exception ex, Logger logger, bool termin
 
             return ex;
         }
+
+        public static string CheckEmpty(this string str) => string.IsNullOrEmpty(str) ? null : str;
     }
 }

src/Forms/SubjectStorageInfoGettingWindow.cs

@@ -33,7 +33,7 @@ public SubjectStorageInfo GetResult(SubjectStorageInfo info = null)
 
         private void ButtonGettingPath_Click(object sender, EventArgs e)
         {
-            textBoxPath.Text = FolderBrowserDialogUtilities.GetFilePath();
+            textBoxPath.Text = FolderBrowserDialogUtilities.GetFilePath() ?? textBoxPath.Text;
         }
 
         private void ButtonOK_Click(object sender, EventArgs e)

src/Forms/WindowMain.cs

@@ -47,7 +47,7 @@ private void ListViewSubjectStorageInfos_ColumnWidthChanging(object sender, Colu
 
         private void ButtonGettingCoursewareSortingSearchingPath_Click(object sender, EventArgs e)
         {
-            textBoxCoursewareSortingSearchingPath.Text = FolderBrowserDialogUtilities.GetFilePath();
+            textBoxCoursewareSortingSearchingPath.Text = FolderBrowserDialogUtilities.GetFilePath() ?? textBoxCoursewareSortingSearchingPath.Text;
             UpdateSubjectStorageInfoConfig();
         }
 

src/Utilities/FolderBrowserDialogUtilities.cs

@@ -16,7 +16,7 @@ public static string GetFilePath(string description = "")
             var dialog = new FolderBrowserDialog() { Description = description };
             dialog.ShowDialog();
 
-            return dialog.SelectedPath;
+            return dialog.SelectedPath.CheckEmpty();
         }
     }
 }