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I was reading this nice article about basic event handling in sharepoint http://karinebosch.wordpress.com/walkthroughs/event-receivers-walkthrough1/ but while doing the exercise a question arised: Why should I call the column as "Title" both in the CAML query and the properties, even if I renamed it before to be called "Planet". If I use "Planet", the event does not fire the correct behavior (an error message).

Here is the piece of code:

public override void  ItemAdding(SPItemEventProperties properties)
{
    // get the name of the planet that needs to be saved
    string planet = properties.AfterProperties["Title"].ToString();

     using (SPWeb web = properties.OpenWeb())

    {

      // get the Planet list (will be queried for existing planet name)

      SPList list = web.Lists[properties.ListId];



   // build the query

   SPQuery query = new SPQuery();

       query.Query = string.Format("<Where><Eq><FieldRef Name=\"Title\" /><Value Type=\"Text\">{0}</Value></Eq></Where>", planet);



   // execute the query

   SPListItemCollection items = list.GetItems(query);

   if (items != null && items.Count > 0)

   {

       properties.ErrorMessage = string.Format(

         "The planet with the name {0} already exists.", planet);

       properties.Status = SPEventReceiverStatus.CancelWithError;

       properties.Cancel = true;
   }
}

}

Also, what implications have using this code, not in a custom list but in a document library, where you have to upload the file first and then fill up the required metadata. Should the event handling method change in this case to validate metadata?

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This is because in both places of code it is expecting internal name of the field. You should provide the internal name.

First get the internal name of your field and then user it both places of your code

string planetFieldInternalName = properties.List.Fields["Planet"].InternalName;

Following is the example code for getting your 'Planet' field value.

properties.AfterProperties[planetFieldInternalName].ToString();

For CAML query you can fix it by following way:

query.Query = string.Format("<Where><Eq><FieldRef Name=\"{0}\" /><Value Type=\"Text\">{1}</Value></Eq></Where>",planetFieldInternalName, planet);

For the validation part you should check for validation when being added "ItemAdding" and "ItemUpdating".
For the document library ItemAdded fires first when document is added and before meta data is set.
So overall you should check "ItemAdding" for the list and "ItemUpdating" for list and document library.

  • thanks, nice explanation. I went further, by coding a simple solution that would allow me to get those internal names for a given list or document library. – madprofessor Sep 16 '13 at 0:30

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