Displaying the data in gridview if selected all form drop down list

create table Users
(
EmpID int primary key identity(1,1),
UserID int ,
BatchName varchar(40),
)

create table MTWorkStatus
(
TraineeID int,
LineCount int,
AudioID int,
ReviewStatus varchar(40),
CreatedDate datetime,
Completed varchar(40),
cretedby varchar(40)
)

select * from subjectItems

create table subjectItems
(
AuditoName varchar(40)
)
alter table subjectItems add id varchar(40)

update subjectItems set id=1

create table Batches
(
ID int primary key identity(1,1),
BatchNo varchar(40)
)

Insert into Batches values('9-11'),('11-1'),('1-3')
Insert into subjectItems values('A'),('B'),('C')
Insert into MTWorkStatus values(1,1,1,'A',GETDATE(),'ACT',1)
Insert into MTWorkStatus values(2,2,2,'B',GETDATE(),'ACT',2)

Insert into Users values(1,'Batch1'),(2,'Batch2')

Insert into Users values(1,1,1),(2,2,2)

alter table USERS add state int 

public void Bindgrid()
        {
            lblerrmsg.Text = "";
            string query = "select Mts.LineCount,Mts.AudioID,Mts.ReviewStatus,convert(varchar(10), mts.CreatedDate,101) as CreatedDate,u.UserID,si.AuditoName from MTWorkStatus Mts,users u,subjectItems si where " +
            "u.BatchName='" + ddlbatchname.SelectedValue + "' and u.empid='" + ddluser.SelectedValue + "' and Reviewstatus='" + ddlstatus.SelectedItem.Text + "' and mts.TraineeID=u.Empid and si.ID= Mts.AudioID";
            SqlCommand cmd = new SqlCommand(query, con);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            da.Fill(dt);
            dt.Columns.Add("HyperLink", typeof(string));
            // dtfill.Columns.Add("httppath", typeof(string));
            foreach (DataRow row in dt.Rows)
            {
                row["HyperLink"] = "NOT DONE";
            }
            for (int i = 0; i <= dt.Rows.Count - 1; i++)
            {
                string ReviewStatus = dt.Rows[i]["ReviewStatus"].ToString();
                if (ReviewStatus == "True")
                {
                    dt.Rows[i]["HyperLink"] = "DONE";
                }
            }
            dt.AcceptChanges();
            grdbatch.DataSource = dt;
            grdbatch.DataBind();
        }

protected void ddlbatch_OnSelectedIndexChanged(object sender, EventArgs  e)
{
           DataSource ds=//get data from db, pass batch id from dropdownlist as input parameter and get the user details from database 
           ddlUser.DataSource=ds;
           ddlUser.DataTextField="UserName";
           ddlUser.DataValueField="UserId";
           ddlUser.DataBind();
}

protected void btnGo_Click(object sender, EventArgs e)
{
           BindGrid();
}

protected void BindGrid()
{
           DataSet ds=//pass ddlbatch, ddlUser, ddlStatus values as input parameters and fetch data from database.
            gv.DataSource=ds;
            gv.DataBind();
}

create procedure proc_name
(
          @batch varchar(100)=null,
          @user varchar(100)=null,
           @status varchar(100)=null
)
as
begin
            select TextField, ValueField
            from tablename
            where (Col1 = @batch OR @batch IS NULL)
                           and (Col2 = @user OR @user IS NULL)
                           and (Col3 = @status OR @status IS NULL)
end