Problem using stored procedure please help

ALTER PROCEDURE [dbo].[SearchEmployee](@countryid int=null, @cityid int=null,@branchid int=null,@deptid int=null)


AS
BEGIN
    select distinct e.EMPLOYEE_ID, e.DEPARTMENT_ID,e.FIRST_ENAME, e.LAST_ENAME, e.MOBILE_NO, e.LANDLINE, e.EMAIL_ID, e.ADDRESS from EMPLOYEE_INFO e, BRANCH_MASETR b, DEPARTMENT_MASTER d, EMPLOYEE_PICTURE EP

    where (e.BRANCH_ID=b.BRANCH_ID)and
   

    (e.EMPLOYEE_ID=EP.EMPLOYEE_ID) and

    (b.COUNTRY_ID=@countryid or ISNULL(@countryid, -1) = -1 ) and
    (b.CITY_ID=@cityid or ISNULL(@cityid, -1) = -1 ) and
    (e.BRANCH_ID=@branchid or ISNULL(@branchid, -1) = -1 ) AND
    (e.DEPARTMENT_ID=@deptid or ISNULL(@deptid, -1) = -1)

END

DataSet dsserachemp = new DataSet();
      string countryid = Ddlcountry.SelectedValue.ToString();
      string cityid = DdlCity.SelectedValue.ToString();
      string branchid= DdlBranch.SelectedValue.ToString();
      string deptid = DdlDepartment.SelectedValue.ToString();
      dsserachemp = bl.BsearchEmp(countryid, cityid, branchid, deptid);
      GridView1.DataSource = dsserachemp;
      GridView1.DataBind();

public DataSet BsearchEmp(string countryid, string cityid, string branchid, string deptid)
   {
       return Dl.searchemp(countryid, cityid, branchid, deptid);
   }

public DataSet searchemp(string countryid, string cityid,string branchid,string deptid)
   {
       if (cn.State.Equals(ConnectionState.Open)) cn.Close();

       cn.Open();
       cmd = new SqlCommand("SearchEmployee", cn);
       cmd.Parameters.AddWithValue("@countryid", countryid);
       cmd.Parameters.AddWithValue("@cityid", cityid);
       cmd.Parameters.AddWithValue("@branchid", branchid);
       cmd.Parameters.AddWithValue("@deptid", deptid);
       da = new SqlDataAdapter(cmd);
       DataSet dssearch = new DataSet();
       da.Fill(dssearch);
       return dssearch;