Update ListItem

Question

Solved it with a hiddenfield control:

    public void MyData(string prod)
    {
        SPWeb web = SPContext.Current.Web;
        SPList myList = web.Lists.TryGetList("YourList");

        if (myList!=null)
        {
            SPQuery query = new SPQuery();
            query.Query = string.Format(
                "<Where><BeginsWith><FieldRef Name='ProductNumber' />" +
                "<Value Type='Text'>{0}</Value></BeginsWith></Where>", prod);
            query.RowLimit = 10;

            SPListItemCollection items = myList.GetItems(query);

            foreach (SPListItem listItem in items)
            {
                TextBox_NameList.Text = listItem["Title"] != null ? listItem["Title"].ToString() : string.Empty;
                TextBox_ListPriceList.Text = listItem["ListPrice"] != null ? listItem["ListPrice"].ToString() : string.Empty;
                TextBox_ProdNumList.Text = listItem["ProductNumber"] != null ? listItem["ProductNumber"].ToString() : string.Empty;
                TextBox_ColorList.Text = listItem["Color"] != null ? listItem["Color"].ToString() : string.Empty;
                TextBox_MoreInformationList.Text = listItem["MoreInformation"] != null ? listItem["MoreInformation"].ToString() : string.Empty;
                HiddenField_ID.Value = listItem["ID"].ToString();
            }
        }
    }

My button code:

        protected void Button_UpdateProd_Click(object sender, EventArgs e)
    {
        SPWeb web = SPContext.Current.Web;
         //web.AllowUnsafeUpdates = true;

        SPList myList = web.Lists["Extern Products"];
        int listItemId = Convert.ToInt32(HiddenField_ID.Value);

        //Considering you have the ID of the List Item
         SPListItem itemToUpdate = myList.GetItemById(listItemId);

        if(itemToUpdate != null)
        {
            itemToUpdate["Title"] = TextBox_NameList.Text;
            itemToUpdate["ProductNumber"] = TextBox_ProdNumList.Text;
            itemToUpdate["Color"] = TextBox_ColorList.Text;
            itemToUpdate["ListPrice"] = TextBox_ListPriceList.Text;
            itemToUpdate["MoreInformation"] = TextBox_MoreInformationList.Text;

            itemToUpdate.Update();

            TextBox_NameList.Text = string.Empty;
            TextBox_ListPriceList.Text = string.Empty;
            TextBox_ProdNumList.Text = string.Empty;
            TextBox_ColorList.Text = string.Empty;
            TextBox_MoreInformationList.Text = string.Empty;
       }
    }

Hope it helps.

Answer 1

You don't need to save the ID, its automatically generated for you! "ID" is a read-only column, and it gets auto-increment each time you add a new item!

Where you have all the textboxes, take a HiddenField there, name it accordingly!

public void MyData(string prod)
{
    SPWeb web = SPContext.Current.Web;
    SPList myList = web.Lists.TryGetList("YourList");

    if (myList!=null)
    {
        SPQuery query = new SPQuery();
        query.Query = string.Format(
            "<Where><BeginsWith><FieldRef Name='ProductNumber' />" +
            "<Value Type='Text'>{0}</Value></BeginsWith></Where>", prod);
        query.RowLimit = 10;

        SPListItemCollection items = myList.GetItems(query);

        foreach (SPListItem listItem in items)
        {
            TextBox_NameList.Text = listItem["Title"] != null ? listItem["Title"].ToString() : string.Empty;
            TextBox_ListPriceList.Text = listItem["ListPrice"] != null ? listItem["ListPrice"].ToString() : string.Empty;
            TextBox_ProdNumList.Text = listItem["ProductNumber"] != null ? listItem["ProductNumber"].ToString() : string.Empty;
            TextBox_ColorList.Text = listItem["Color"] != null ? listItem["Color"].ToString() : string.Empty;
            TextBox_MoreInformationList.Text = listItem["MoreInformation"] != null ? listItem["MoreInformation"].ToString() : string.Empty;
            HiddenField_ID.Value = listItem["ID"].ToString();
        }
    }
}

Then on Update button click

SPWeb web = SPContext.Current.Web;
    //web.AllowUnsafeUpdates = true;

 SPList myList = web.Lists["Extern Products"];
 int listItemId = Convert.ToInt32(HiddenField.Value);

 //Considering you have the ID of the List Item
 SPListItem itemToUpdate = myList.GetItemById(listItemId);

    if(itemToUpdate != null)
    {

            listItem["Title"] = TextBox_NameList.Text;
            listItem["ProductNumber"] = TextBox_ProdNumList.Text;
            listItem["Color"] = TextBox_ColorList.Text;
            listItem["ListPrice"] = TextBox_ListPriceList.Text;
            listItem["MoreInformation"] = TextBox_MoreInformationList.Text;

            listItem.Update();

            TextBox_NameList.Text = string.Empty;
            TextBox_ListPriceList.Text = string.Empty;
            TextBox_ProdNumList.Text = string.Empty;
            TextBox_ColorList.Text = string.Empty;
            TextBox_MoreInformationList.Text = string.Empty;

   }

For delete simply use listItem.Delete(); instead of listItem.Update();

You don't need SPQuery in this case, since it is one Item you want to update and you have the ID for it!

Extra Information on SPQuery

Here is list of all operations available in CAML Query
Query Schema

For ease in CAML Queries, you can try one of the CAML Query Builders:
http://spcamlqueryhelper.codeplex.com/
http://www.u2u.net/res/Tools/CamlQueryBuilder.aspx

I hope this helps