Update current item [duplicate]

Question

I am trying to update current items, but all items in the list get updated why?

 public override void ItemAdding(SPItemEventProperties properties)
    {
        using (SPWeb web = properties.OpenWeb())
        {

            SPList myList = web.Lists.TryGetList("DocumentList");
            SPListItemCollection itemCollection = myList.Items;
            web.AllowUnsafeUpdates = true;

            for (int iCount = 0; iCount < itemCollection.Count; iCount++)
            {

                SPListItem _item = itemCollection[iCount];

                _item["MyField"] = "";
                _item.Update();
            }




        }}

Answer 1

You can modify item properties, except ID like this.

public override void ItemAdding(SPItemEventProperties properties)
{
    string mycol_internal = "";

    using (SPWeb web = properties.OpenWeb()) {
        mycol_internal = web.Lists[properties.ListId].Fields["My Column"].InternalName;
    }

    properties.AfterProperties[mycol_internal] = "your new value";

    //Update title with another column value etc
    properties.AfterProperties["Title"] = properties.AfterProperties[mycol_internal].ToString();
}

Source

OR, use ItemAdded where properties.ListItem is available.

Answer 2

In the code you have written a for loop which is looping all the items in the list. So for every item it is updating the column value until it reaches the last list item count. Use properties.ListItem to update the current item in which you have ItemAdding event will fire.