Q) What's Wrong in this? Getting "NullReferenceObject Exception"

C#:
I have getting "System.NullReferenceException: Object refernce not set to an instance of an object, at" .
This Exception is getting when giving the some text into the textbox's & Clicking Button of Windows Control Library form (usercontrol) which is placed the UC_submitcontrol usercontrol on the UCTestApp1 Windows Form and Execute.

See the Pictures:



Code for UC_SubmitControl1:

namespace UC_SubmitControl1
{
    public partial class UC_SubmitScreen : UserControl
    {
        public delegate void SubmitClickHandler();
        public event SubmitClickHandler SubmitbtnClicked;

        public UC_SubmitScreen()
        {
            InitializeComponent();
        }

        private void btnSubmit_Click(object sender, EventArgs e)
        {
            if(tbText.Text.Length==0)
                MessageBox.Show("Please Enter Some Text..!");
            else
            {
                OnSubmitClicked();
            }
        }

        protected virtual void OnSubmitClicked()
        {
            if (SubmitbtnClicked != null)
            {
                SubmitbtnClicked();  // Notify Subscribers
            }
        }

        public string Prop_TextHere
        {
            get { return tbText.Text; }
            set { tbText.Text = value;  }
        }
    }
}

See the Picture for UC_TestApp1 [Windows Application]


Code for UC_TestApp1:

namespace UC_TestApp1
{
    public partial class Form1 : Form
    {
        private UC_SubmitControl1.UC_SubmitScreen submitscrObj;
        //private System.ComponentModel.Container components = null;


        public Form1()
        {
            InitializeComponent();
        }

        private void uC_SubmitScreen1_SubmitbtnClicked()
        {
            try
            {
                MessageBox.Show(String.Format("Hello, {0}!", submitscrObj.Prop_TextHere));
                //string aa = submitscrObj.Prop_TextHere;
                //MessageBox.Show("Hello ", +aa.ToString()+" !");
                //this.Close();
            }
            catch (Exception e)
            {
                MessageBox.Show(e.ToString());
                this.Close();
            }
        }        
    }        
}