Gridview rowupdating problem

<asp:TemplateField HeaderText="Subject/Description" SortExpression="SubjectDescription" ItemStyle-Wrap="false">
    <ItemTemplate >
        <asp:Label ID="lblSubjectDescriptione" runat="server" Text='<%# Eval("SubjectDescription") %>' />
    </ItemTemplate>
    <EditItemTemplate >
        <asp:TextBox id="SubjectDescription" runat="server" Text='<%# Bind("SubjectDescription") %>'/>
    </EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Responsible Person" SortExpression="ResponsiblePerson" ItemStyle-Wrap="false">
    <ItemTemplate >
        <asp:Label ID="lblResponsiblePerson" runat="server" Text='<%# Eval("ResponsiblePerson") %>' />
    </ItemTemplate>
    <EditItemTemplate >
        <asp:TextBox id="ResponsiblePerson" runat="server" Text='<%# Bind("ResponsiblePerson") %>'/>
    </EditItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="PriorityLevel" HeaderText="Priority Level" ReadOnly="True" HeaderStyle-Wrap="false" /> 
<asp:TemplateField HeaderText="Final Response Due Date" SortExpression="FinalResponseDueDate" ItemStyle-Wrap="false">
    <ItemTemplate >
        <asp:Label ID="lblFinalResponseDueDate" runat="server" Text='<%# Eval("FinalResponseDueDate", "{0:d}") %>' />
    </ItemTemplate>
    <EditItemTemplate >
        <asp:TextBox id="FinalResponseDueDate" runat="server" Text='<%# Bind("FinalResponseDueDate", "{0:d}") %>'/>
    </EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Completion Date" SortExpression="CompletionDate" ItemStyle-Wrap="false">
    <ItemTemplate >
        <asp:Label ID="lblCompletionDate" runat="server" Text='<%# Eval("CompletionDate", "{0:d}") %>' />
    </ItemTemplate>
    <EditItemTemplate >
        <asp:TextBox id="CompletionDate" runat="server" Text='<%# Bind("CompletionDate", "0:d}") %>'/>
    </EditItemTemplate>
</asp:TemplateField>

        protected void gvCARs_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {
            try
            {
                using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["aero"].ToString()))
                {
                    using (SqlCommand cmd = new SqlCommand("dbo.spx_UpdateCAR", conn))
                    {

                        cmd.Connection = conn;

                        //cmd.CommandText = "UPDATE Aerospace.dbo.CARLog SET SubjectDescription = @SubjectDescription, ResponsiblePerson = @ResponsiblePerson, CompletionDate = @CompletionDate WHERE CAR# = @CAR";

                        cmd.CommandType = CommandType.StoredProcedure;

                        // Get the Visa Index of the selected row.
                        HiddenField lbl = (HiddenField)gvCARs.Rows[e.RowIndex].FindControl("CARID");
                        string strSubjectDescription = ((TextBox)gvCARs.Rows[e.RowIndex].FindControl("SubjectDescription")).Text;
                        string strResponsiblePerson = ((TextBox)gvCARs.Rows[e.RowIndex].FindControl("ResponsiblePerson")).Text;
                        string strFinalResponseDueDate = ((TextBox)gvCARs.Rows[e.RowIndex].FindControl("FinalResponseDueDate")).Text;
                        string strCompletionDate = ((TextBox)gvCARs.Rows[e.RowIndex].FindControl("CompletionDate")).Text;
                        if (string.IsNullOrEmpty(strCompletionDate))
                            strCompletionDate = "none";
                        if (string.IsNullOrEmpty(strResponsiblePerson))
                            strResponsiblePerson = "none";
                        if (string.IsNullOrEmpty(strFinalResponseDueDate))
                            strFinalResponseDueDate = "none";
                        if (string.IsNullOrEmpty(strSubjectDescription))
                            strSubjectDescription = "none";

                        Response.Write("CAR: " + lbl.Value + "<BR>");
                        Response.Write("FinalResponseDueDate: " + strFinalResponseDueDate + "<br>");
                        Response.Write("ResponsiblePerson: " + strResponsiblePerson + "<br>");
                        Response.Write("Completion Date: " + strCompletionDate + "<br>");
                        Response.Write("Subject/Description: " + strSubjectDescription);

                        // Append the parameters.
                        cmd.Parameters.AddWithValue("@CAR", lbl.Value);
                        cmd.Parameters.AddWithValue("@SubjectDescription", strSubjectDescription);
                        cmd.Parameters.AddWithValue("@ResponsiblePerson", strResponsiblePerson);
                        cmd.Parameters.AddWithValue("@FinalResponseDueDate", strFinalResponseDueDate);
                        cmd.Parameters.AddWithValue("@CompletionDate", strCompletionDate);

                        // Open the connection.
                        conn.Open();

                        // Execute the command.
                        cmd.ExecuteNonQuery();
                    }
                }

            // NOTE: The nested using {... } directives in these methods will automatically close and dispose both Command and Connection objects.
            // It is the equivalent of wrapping the code in a try / finally block.

            // Exit edit mode.
            gvCARs.EditIndex = -1;

            // Rebind the GridView control to show data after updating.
            BindGridView();

            // Show the Add button.
            lbtnAdd.Visible = true;
        }
            catch (Exception ex)
            {
                Label1.Text = "Error in execution " + ex.ToString();
            }
        }