About the save field

Hello

I have two "Save" buttons. one of implement way is:

<SharePoint:SaveButton ID="SaveButton1" runat="server" Text="Save" CssClass="CommonButton" />

another is:

<asp:Button ID="Save" runat="server" Text="My Save Button" CssClass="CommonButton" OnClick="Save_Click" />

in "OnClick" event, i use "Item.Update()" method to save item.

in form, i use "<SharePoint:FormField ID="de="New" FieldName="SR"   runat="server" DisplaySize="32" />" to represent field.

I have some checkbox and radio controls, i need to write these controls value to specify fields when save item.

Now , i have a problem.

When i use "Save" button to save item, i can't write these controls value to specify fields and others fields can save.

When i use "My Save Button" button to save item, only these controls value can save, others fields can not save.

So, any idea not only can write these controls value but also save others fields?

Thanks in advance!