little change

WinFormControl/UScanPanel.cs

@@ -7,6 +7,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Windows.Forms;
+using WinFormControl.Converter;
 
 namespace WinFormControl
 {
@@ -32,9 +33,13 @@ namespace WinFormControl
     protected override void OnLoad(EventArgs e)
     {
       base.OnLoad(e);
-      if (!ParentForm.KeyPreview)
-        ParentForm.KeyPreview = true;
-      ParentForm.KeyPress += ParentForm_KeyPress;
+      var parentForm = ControlUtil.GetParentFormm(this);
+      if (parentForm != null)
+      {
+        if (!parentForm.KeyPreview)
+          parentForm.KeyPreview = true;
+        parentForm.KeyPress += ParentForm_KeyPress;
+      }
     }
 
     bool reading = false;

WinFormControl/UWeightControl.cs

@@ -11,6 +11,7 @@ using WinFormControl.Properties;
 using System.Threading;
 using System.IO.Ports;
 using System.Collections.Concurrent;
+using WinFormControl.Converter;
 
 namespace WinFormControl
 {
@@ -42,13 +43,17 @@ namespace WinFormControl
     protected override void OnLoad(EventArgs e)
     {
       base.OnLoad(e);
-      ParentForm.FormClosing += delegate
+      var parentForm = ControlUtil.GetParentFormm(this);
+      if (parentForm != null)
       {
-        if (_inQueryThread != null && _inQueryThread.IsAlive)
+        parentForm.FormClosing += delegate
         {
-          DisableWeight();
-        }
-      };
+          if (_inQueryThread != null && _inQueryThread.IsAlive)
+          {
+            DisableWeight();
+          }
+        };
+      }
     }
 
     private void settingBtn_Click(object sender, EventArgs e)