GridView Edit/Delete and Bind

Html Section:

<asp:GridView ID="grdvBook" runat="server" AutoGenerateColumns="false" OnRowDataBound="grdvBook_RowDataBound"
    OnRowEditing="grdvBook_RowEditing" OnRowCancelingEdit="grdvBook_RowCancelingEdit"
    OnRowUpdating="grdvBook_RowUpdating" OnRowDeleting="grdvBook_RowDeleting">
   <Columns>
       <asp:TemplateField HeaderText="Author">
           <ItemTemplate>
               <asp:Label ID="lblBookId" runat="server" Visible="false"></asp:Label>
               <asp:Label ID="lblAuthor" runat="server"></asp:Label>
           </ItemTemplate>
           <EditItemTemplate>
               <asp:TextBox ID="txtBookId" runat="server" Visible="false"></asp:TextBox>
               <asp:TextBox ID="txtAuthor" runat="server"></asp:TextBox>
           </EditItemTemplate>
           <ControlStyle Width="125px"></ControlStyle>
       </asp:TemplateField>
       <asp:TemplateField HeaderText="ISBN">
           <ItemTemplate>
               <asp:Label ID="lblISBN" runat="server"></asp:Label>
           </ItemTemplate>
           <EditItemTemplate>
               <asp:TextBox ID="txtISBN" runat="server"></asp:TextBox>
           </EditItemTemplate>
           <ControlStyle Width="80px"></ControlStyle>
       </asp:TemplateField>
       <asp:TemplateField HeaderText="Year">
           <ItemTemplate>
               <asp:Label ID="lblYear" runat="server"></asp:Label>
           </ItemTemplate>
           <EditItemTemplate>
               <asp:TextBox ID="txtYear" runat="server"></asp:TextBox>
           </EditItemTemplate>
           <ControlStyle Width="40px"></ControlStyle>
       </asp:TemplateField>
       <asp:TemplateField HeaderText="Title">
           <ItemTemplate>
               <asp:Label ID="lblTitle" runat="server"></asp:Label>
           </ItemTemplate>
           <EditItemTemplate>
               <asp:TextBox ID="txtTitle" runat="server"></asp:TextBox>
           </EditItemTemplate>
           <ControlStyle Width="125px"></ControlStyle>
       </asp:TemplateField>
       <asp:TemplateField HeaderText="Edition">
           <ItemTemplate>
               <asp:Label ID="lblEdition" runat="server"></asp:Label>
           </ItemTemplate>
           <EditItemTemplate>
               <asp:TextBox ID="txtEdition" runat="server"></asp:TextBox>
           </EditItemTemplate>
       </asp:TemplateField>
       <asp:TemplateField HeaderText="Edit">
           <ItemTemplate>
               <asp:ImageButton ID="imgEdit" runat="server" ToolTip="Edit Information" CommandName="Edit"
                   ImageUrl="~/images/edit_icon.png" />
           </ItemTemplate>
           <EditItemTemplate>
               <asp:ImageButton ID="imgSave" runat="server" ImageUrl="~/images/AddEvidence.png"
                   ToolTip="Save" />
               <asp:ImageButton ID="imgCancle" runat="server" ImageUrl="~/images/cancel_icon.png"
                   ToolTip="Cancel" />
           </EditItemTemplate>
       </asp:TemplateField>
       <asp:TemplateField HeaderText="Delete">
           <ItemTemplate>
               <asp:ImageButton ID="imgDelte" runat="server" ImageUrl="~/images/Cross.png" CommandName="Delete" />
           </ItemTemplate>
       </asp:TemplateField>
   </Columns>
</asp:GridView>

C # Coding Section:

protected void grdvBook_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        Label lblBookId = (Label)e.Row.FindControl("lblBookId");
        Label lblAuthor = (Label)e.Row.FindControl("lblAuthor");
        Label lblISBN = (Label)e.Row.FindControl("lblISBN");
        Label lblYear = (Label)e.Row.FindControl("lblYear");
        Label lblTitle = (Label)e.Row.FindControl("lblTitle");
        Label lblEdition = (Label)e.Row.FindControl("lblEdition");

        ImageButton imgEdit = (ImageButton)e.Row.FindControl("imgEdit");
        ImageButton imgDelte = (ImageButton)e.Row.FindControl("imgDelte");

        if (lblBookId != null)
            lblBookId.Text = ((LINQ.Book)e.Row.DataItem).BookId.ToString();

        if (lblAuthor != null)
            lblAuthor.Text = ((LINQ.Book)e.Row.DataItem).Author.ToString();

        if (lblISBN != null)
            lblISBN.Text = ((LINQ.Book)e.Row.DataItem).ISBN.ToString();

        if (lblYear != null)
            lblYear.Text = ((LINQ.Book)e.Row.DataItem).Year.ToString();

        if (lblTitle != null)
            lblTitle.Text = ((LINQ.Book)e.Row.DataItem).Title.ToString();

        if (lblEdition != null)
            lblEdition.Text = ((LINQ.Book)e.Row.DataItem).Edition.ToString();

        if (imgEdit != null)
        {
            imgEdit.CommandArgument = ((LINQ.Book)e.Row.DataItem).BookId.ToString();
            imgEdit.CommandName = "Edit";
        }

        if (imgDelte != null)
        {
            imgDelte.CommandArgument = ((LINQ.Book)e.Row.DataItem).BookId.ToString();
            imgDelte.CommandName = "Delete";
        }


        TextBox txtBookId = (TextBox)e.Row.FindControl("txtBookId");
        TextBox txtAuthor = (TextBox)e.Row.FindControl("txtAuthor");
        TextBox txtISBN = (TextBox)e.Row.FindControl("txtISBN");
        TextBox txtYear = (TextBox)e.Row.FindControl("txtYear");
        TextBox txtTitle = (TextBox)e.Row.FindControl("txtTitle");
        TextBox txtEdition = (TextBox)e.Row.FindControl("txtEdition");

        ImageButton imgSave = (ImageButton)e.Row.FindControl("imgSave");
        ImageButton imgCancle = (ImageButton)e.Row.FindControl("imgCancle");

        if (txtBookId != null)
            txtBookId.Text = ((LINQ.Book)e.Row.DataItem).BookId.ToString();

        if (txtAuthor != null)
            txtAuthor.Text = ((LINQ.Book)e.Row.DataItem).Author.ToString();

        if (txtISBN != null)
            txtISBN.Text = ((LINQ.Book)e.Row.DataItem).ISBN.ToString();

        if (txtYear != null)
            txtYear.Text = ((LINQ.Book)e.Row.DataItem).Year.ToString();

        if (txtTitle != null)
            txtTitle.Text = ((LINQ.Book)e.Row.DataItem).Title.ToString();

        if (txtEdition != null)
            txtEdition.Text = ((LINQ.Book)e.Row.DataItem).Edition.ToString();

        if (imgSave != null)
            imgSave.CommandName = "Update";

        if (imgCancle != null)
            imgCancle.CommandName = "Cancel";
    }
}

protected void grdvBook_RowEditing(object sender, GridViewEditEventArgs e)
{
    grdvBook.EditIndex = e.NewEditIndex;
    grdvBook.Columns[5].HeaderText = "Update";
    grdvBook.Columns[6].Visible = false;
    imgAddBook.Visible = false;
    ShowTempBooks();
}

protected void grdvBook_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
{
    grdvBook.EditIndex = -1;
    grdvBook.Columns[5].HeaderText = "Edit";
    grdvBook.Columns[6].Visible = true;
    if (Convert.ToInt32(((TextBox)grdvBook.Rows[e.RowIndex].FindControl("txtBookId")).Text) == 0)
    {
        List<LINQ.Book> objBooks = (List<LINQ.Book>)Session["Books"];
        objBooks.RemoveAt(objBooks.Count - 1);
        Session["Books"] = objBooks;
    }
    imgAddBook.Visible = true;
    ShowTempBooks();
}

protected void grdvBook_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
    bool boolError = false;
    int bookId = Convert.ToInt32(((TextBox)grdvBook.Rows[e.RowIndex].FindControl("txtBookId")).Text);
    string author = ((TextBox)grdvBook.Rows[e.RowIndex].FindControl("txtAuthor")).Text;
    string ISBN = ((TextBox)grdvBook.Rows[e.RowIndex].FindControl("txtISBN")).Text;
    string year = ((TextBox)grdvBook.Rows[e.RowIndex].FindControl("txtYear")).Text;
    string title = ((TextBox)grdvBook.Rows[e.RowIndex].FindControl("txtTitle")).Text;
    string edition = ((TextBox)grdvBook.Rows[e.RowIndex].FindControl("txtEdition")).Text;
    if (author == string.Empty)
    {
        Utilities.CreateMessageLabel(this, BLL.Constants.AuthorNameReq, false);
        boolError = true;
    }
    if (ISBN == string.Empty)
    {
        Utilities.CreateMessageLabel(this, BLL.Constants.ISBNReq, false);
        boolError = true;
    }
    if (ISBN != string.Empty)
    {
        try
        {
            Convert.ToInt32(ISBN);
        }
        catch (FormatException ex)
        {
            Utilities.CreateMessageLabel(this, BLL.Constants.ISBNNumeric, false);
            boolError = true;
        }
    }
    if (year == string.Empty)
    {
        Utilities.CreateMessageLabel(this, BLL.Constants.YearReq, false);
        boolError = true;
    }
    if (year != string.Empty)
    {
        try
        {
            Convert.ToInt32(year);
        }
        catch (FormatException ex)
        {
            Utilities.CreateMessageLabel(this, BLL.Constants.YearNemeric, false);
            boolError = true;
        }
        if (year.Length > 4)
        {
            Utilities.CreateMessageLabel(this, BLL.Constants.YearLength, false);
            boolError = true;
        }
    }
    if (title == string.Empty)
    {
        Utilities.CreateMessageLabel(this, BLL.Constants.BookTitleReq, false);
        boolError = true;
    }
    if (edition == string.Empty)
    {
        Utilities.CreateMessageLabel(this, BLL.Constants.EditionReq, false);
        boolError = true;
    }
    if (!boolError)
    {
        List<LINQ.Book> objBooks = (List<LINQ.Book>)Session["Books"];
        LINQ.Book objBook = null;
        if (bookId > 0)
        {
            objBook = objBooks.Where(B => B.BookId == bookId).Single();
            objBook.CourseId = Convert.ToInt32(Session[Constants.ProgramSessionValues.courseId.ToString()]);
            objBook.Author = author;
            objBook.ISBN = ISBN;
            objBook.Title = title;
            objBook.Year = year;
            objBook.Edition = edition;
        }
        else
        {
            objBook = objBooks.ElementAt(e.RowIndex);
            objBook.CourseId = Convert.ToInt32(Session[Constants.ProgramSessionValues.courseId.ToString()]);
            objBook.Author = author;
            objBook.ISBN = ISBN;
            objBook.Title = title;
            objBook.Year = year;
            objBook.Edition = edition;
        }
        Session["Books"] = objBooks;
        grdvBook.EditIndex = -1;
        grdvBook.Columns[5].HeaderText = "Edit";
        grdvBook.Columns[6].Visible = true;
        imgAddBook.Visible = true;
        ShowTempBooks();
    }
    else
    {
        grdvBook.EditIndex = e.RowIndex;
    }
}

protected void grdvBook_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
    List<LINQ.Book> objBooks = (List<LINQ.Book>)Session["Books"];

    objBooks.RemoveAt(e.RowIndex);
    Session["Books"] = objBooks;
    ShowTempBooks();
}

protected void imgAddBook_Click(object sender, ImageClickEventArgs e)
{
    GenerateBookRow();
}

public void GenerateBookRow()
{
    List<LINQ.Book> objBooks = (List<LINQ.Book>)Session["Books"];
    LINQ.Book objBook = new LINQ.Book();

    objBook.CourseId = Convert.ToInt32(Session[Constants.ProgramSessionValues.courseId.ToString()]);
    objBook.Author = string.Empty;
    objBook.ISBN = string.Empty;
    objBook.Year = string.Empty;
    objBook.Title = string.Empty;
    objBook.Edition = string.Empty;
    objBooks.Add(objBook);
    Session["Books"] = objBooks;
    grdvBook.EditIndex = objBooks.Count - 1;
    grdvBook.Columns[5].HeaderText = "Update";
    grdvBook.Columns[6].Visible = false;
    imgAddBook.Visible = false;
    ShowTempBooks();
}