question

@heyangben-3420 , Welcome to Microsoft Q&A, we could get component list of the form, then we could convert the component to the Tooltip type to call the RemoveAll method.

Here is a code example you could refer to.

   private void button1_Click(object sender, EventArgs e)
         {
             var result = EnumerateComponents();
             foreach (var item in result)
             {
                 if(item is ToolTip)
                 {
                     ToolTip tip = (ToolTip)item;
                     tip.RemoveAll();
                 }
             }
    
         }
    
         private void Form1_Load(object sender, EventArgs e)
         {
             toolTip1.SetToolTip(button1, "Save changes");
             toolTip1.SetToolTip(checkBox1, "Please choose");
    
         }
    
         private IEnumerable<Component> EnumerateComponents()
         {
             return from field in GetType().GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)
                    where typeof(Component).IsAssignableFrom(field.FieldType)
                    let component = (Component)field.GetValue(this)
                    where component != null
                    select component;
         }

Result:

Best Regards,
Jack

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