How to delete a row from a dataTable and adjust a cost

Hello,
 I am working on a basic shopping cart that will allow users to register for an event. I have built the cart using a dataTable and I have been able to add the users as well as calculate a running total. I am having difficulty though figuring out how to delete a row from the shopping cart. If a user decides they want to remove an attendee I want them to be able to click on a remove link in my datagrid and remove the user. This function should remove the row as well as adjust the total cost.
I have built a similar page in vb.net but I am having trouble translating the code over to C#.net  When I try to call the dataTable from another function I get an error that the dataTable name does not exist in the current context.

Can you please help me understand what I am missing and how to correct this so that I am able to remove items from my shopping cart.
Thanks in advance,

//create shopping cart
    private void DataTable()
    {
        DataTable MyDT = new DataTable();
        DataRow MyRow;
 
        if (ViewState["DataTable"] == null)
        {
            MyDT.Columns.Add("regID", System.Type.GetType("System.Int32"));
            MyDT.Columns.Add("Fname");
            MyDT.Columns.Add("Lname");
            MyDT.Columns.Add("Title");
            MyDT.Columns.Add("Agency");
            MyDT.Columns.Add("Email");
            MyDT.Columns.Add("Shirt");
            MyDT.Columns.Add("FstAtt");
            MyDT.Columns.Add("Price", typeof(Decimal));
            MyRow = MyDT.NewRow();
            MyRow[0] = MyDT.Rows.Count + 1;
            MyRow[1] = TxtFName.Text;
            MyRow[2] = TxtLName.Text;
            MyRow[3] = TxtTitle.Text;
            MyRow[4] = TxtAgency.Text;
            MyRow[5] = TxtEmail.Text;
            MyRow[6] = ddShirt.SelectedItem.Text;
            MyRow[7] = ddAttend.SelectedItem.Text;
            MyRow[8] = 100; //current rate for User Conference registration
            MyDT.Rows.Add(MyRow);
            //clear fields
            TxtFName.Text = "";
            TxtLName.Text = "";
            TxtTitle.Text = "";
            TxtAgency.Text = "";
            TxtEmail.Text = "";
            ddShirt.SelectedIndex = -1;
            ddAttend.SelectedIndex = -1;
            //Calculate Total for Shopping Cart
            Decimal Total = 0.00M;
            foreach (DataRow Row in MyDT.Rows)
            {
                Total += (Decimal)Row["Price"];
            }
            runTotalLBL.Text = Total.ToString();
        }
        else
        {
            MyDT = (DataTable)ViewState["DataTable"];
            MyRow = MyDT.NewRow();
            MyRow[0] = MyDT.Rows.Count + 1;
            MyRow[1] = TxtFName.Text;
            MyRow[2] = TxtLName.Text;
            MyRow[3] = TxtTitle.Text;
            MyRow[4] = TxtAgency.Text;
            MyRow[5] = TxtEmail.Text;
            MyRow[6] = ddShirt.SelectedItem.Text;
            MyRow[7] = ddAttend.SelectedItem.Text;
            MyRow[8] = 100;
            MyDT.Rows.Add(MyRow);
            //clear fields after each registrant is entered
            TxtFName.Text = "";
            TxtLName.Text = "";
            TxtTitle.Text = "";
            TxtAgency.Text = "";
            TxtEmail.Text = "";
            ddShirt.SelectedIndex = -1;
            ddAttend.SelectedIndex = -1;
            //Calculate Total for Shopping Cart
            Decimal Total = 0.0M;
            foreach (DataRow Row in MyDT.Rows)
            {
                Total += (Decimal)Row["Price"];
            }
            runTotalLBL.Text = Total.ToString();
        }
        ViewState["DataTable"] = MyDT;
        //bind datatable to datagrid
        dg.DataSource = MyDT;
        dg.DataBind();
    }
 
    //add attendees to roster datagrid
    protected void AddToCart(object sender, EventArgs e)
    {
        DataTable();
    }
 
    //remove attendee from data grid
    protected void Delete_Item(object source, DataGridCommandEventArgs e)
    {
       //Here is where I get stuck. In vb.net the datatable was recognized across functions however here it only seems to be accessible within the function "DataTable"
        ViewState["DataTable"] = MyDT;
 
 
 
    }

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