Null Reference in editing a task scheduler trigger in c#

if (t != null) is always null why help.. when ever i try to get value in the variable name t it always gets in the else part but i am sure that there is valuse in tat variable.

private void button3_Click(object sender, EventArgs e)
      {
            try
            {
                if (search=="")
                {

            开发者_如何学Go    }
                else
                {
                    if (textBox1.Text=="")
                    {
                        MessageBox.Show("Select A Task Or Find One");
                    }
                    else
                    {
                        search = textBox1.Text;
                    }
                                 }
                if (search != null)
                {
                    t = tasks.OpenTask(search);
                    if (textBox2.Text!="")
                    {

                    short hour = short.Parse(textBox2.Text.Substring(0, 2));
                    short minute = short.Parse(textBox2.Text.Substring(3, 2));
                        if (t != null)  // this is null dont know why
                    {
                        foreach (Trigger tr in t.Triggers)
                        {
                            if (tr is StartableTrigger)
                            {
                                (tr as StartableTrigger).StartHour = hour;
                                (tr as StartableTrigger).StartMinute = minute;
                            }
                        }
                        t.Save();
                        t.Close();
                    }
                    tasks.Dispose();
                    button2.Visible = true;
                    textBox3.Visible = true;
                    search = "";
                    }
                    else
                    {
                        MessageBox.Show("Enter Time ");
                    }
                }
            }
            catch (Exception b)
            {
                MessageBox.Show(b.ToString());
               // MessageBox.Show("Select A Task From The List ");
            } 

        }

help guys .. well i tried it to debug but didnt get a break through..

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t is null because tasks.OpenTask(search) returns null. Probably there is no task matching your search criteria.

Why are you disposing of tasks in the first place?

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Any place in your source ,where you have written something like this MyClass t = new MyClass().. where t is your class object. If you have not declared,It will always come null.

Or might be you have declared something like this private Task t; but forgot to add new keyword. Checkout!!!