.NET FOLLOWER

    After in-place upgrading one of our SharePoint applications, we had been faced with the fact that some content types comprised duplicated fields. In other words, within the several <ContentType> sections of a list’s schema, we could find the pair <FieldRef> nodes with identical identifiers and names. Schematically, it looked like the following:

<?xml version="1.0" encoding="utf-8"?>
<List Name="SomeList" Title="Some List" BaseType="0" Url="Lists/SomeList" 
           Type="100" Id="a5bba3b3-5b1d-4186-ada7-bbd82b17f76d" ...>
  <MetaData>
    <Views>
       ...
    </Views>

    <Fields>
       ...
    </Fields>

    <ContentTypes>
       ...
       <ContentType ID="0x0100078C8A39971A4532AB9C5EB6DCB388A3" Name="SomeContentType" ...>
        <FieldRefs>
           ...
           <FieldRef Name="SomeField" ID="{b986cd1a-8bd0-4072-93af-5c48571bbf56}" />
           ...
           <FieldRef Name="SomeField2" ID="{6d245d53-63ef-4650-b676-6e4ee66dcda5}" />
           ...           
           <FieldRef Name="SomeField2" ID="{6d245d53-63ef-4650-b676-6e4ee66dcda5}" />
           ...   
           <FieldRef Name="SomeField" ID="{b986cd1a-8bd0-4072-93af-5c48571bbf56}" />
           ...
        </FieldRefs>
       ...    
    </ContentTypes>

    <Forms>
       ...
    </Forms>
   </MetaData>
</List>

The reason of such duplication still isn’t clear for me, but I’ve figured out how to get rid of it 🙂 Below is a simple method for deleting the excess fields from a passed content type:

protected static void RemoveDuplicatedFields(SPContentType spContentType)
{
    bool duplicationFound = false;

    // identify how many times every field encounter
    Dictionary<Guid, int> tmpDir = new Dictionary<Guid, int>();
    foreach (SPFieldLink spFieldLink in spContentType.FieldLinks)
        if (!tmpDir.ContainsKey(spFieldLink.Id))
            tmpDir.Add(spFieldLink.Id, 1);
        else
        {
            tmpDir[spFieldLink.Id]++;
            duplicationFound = true;
        }
   

    if (duplicationFound)
        // remove all excess mentions of fields
        foreach (KeyValuePair<Guid, int> keyValuePair in tmpDir)
        {
            int removeIterationCount = keyValuePair.Value - 1;
            for (int i = 0; i < removeIterationCount; i++)
                spContentType.FieldLinks.Delete(keyValuePair.Key);
        }
}