how to pass default value to date parametere in storedprocedure - Sqlserver 2008?

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C#

SQL-Server

**here it is my stored procedure:**

ALTER proc [dbo].[allrecp]
   @peid int=0,
   @pename varchar(20)='',
   @pdes varchar(20)='',
   @pdoj date='1111-1-1',
   @sal money=0,
   @dept int=0,
   @loc int=0,@i int=0
   as begin
   if(@i=1)
   begin
   insert into Employee values(@pename,@pdes,@pdoj,@sal,@dept,@loc)
   end
   if(@i=2)
   begin
   update Employee set ENAME=@pename,DESEGNATION=@pdes,DOJ=@pdoj,SALARY=@sal,DEPTID=@dept,LOCATIONID=@loc WHERE EMPID=@peid
   end
   if(@i=3)
   delete EMPLOYEE where EMPID=@peid
   end

**and my c# code is:**

private void btndelete_Click(object sender, EventArgs e)
            {
                parameteres(3);
            }

            private void btnupdate_Click(object sender, EventArgs e)
            {
                parameteres(2);
            }

            private void BTNINSERT_Click(object sender, EventArgs e)
            {
                parameteres(1);


            }
            public void parameteres(int i)
            {
                cmd = new SqlCommand();
                cmd.Connection = con;
                cmd.CommandText = "allrecp";
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.Add(new SqlParameter("@peid", SqlDbType.Int)).Value = txtempid.Text;
                cmd.Parameters.Add(new SqlParameter("@pename", SqlDbType.VarChar, 20)).Value = txtename.Text;
                cmd.Parameters.Add(new SqlParameter("@pdes", SqlDbType.VarChar, 20)).Value = txtdesg.Text;



                cmd.Parameters.Add(new SqlParameter("@pdoj", SqlDbType.Date)).Value = txtdoj.Text;

here i face the problem is:

Failed to convert parameter value from a String to a DateTime

                cmd.Parameters.Add(new SqlParameter("@dept", SqlDbType.Int)).Value = txtdept.Text;
                cmd.Parameters.Add(new SqlParameter("@sal", SqlDbType.Money)).Value = txtsal.Text;
                cmd.Parameters.Add(new SqlParameter("@loc", SqlDbType.Int)).Value = txtlocation.Text;
                cmd.Parameters.Add(new SqlParameter("@i", SqlDbType.Int)).Value = i;
                con.Open();
                int x = cmd.ExecuteNonQuery();
                con.Close();
                MessageBox.Show(x + " rows effected");
            }
here iam face the problem :
                cmd.Para

meters.Add(new SqlParameter("@dept", SqlDbType.Int)).Value = txtdept.Text;

i.e: Failed to convert parameter value from a String to a DateTime. plz give me solution the solution and how to pass default values in to stored procedure.