Recently, in one of our projects we came across a requirement where in we needed to clear all fields for a list item on an item copy or a checkin.
In order to implement this , we used eventhandlers for ItemCheckedIn and implemented the code to clear all fields, setting all fields to null i.e.
This worked well for all fields except the managed metadata or the taxonomy columns which give an exception while setting the value to null.
In order to clear these columns , we explicitly need to set the properties "WssId, TermGuid and Label" to null as is shown below:
In order to implement this , we used eventhandlers for ItemCheckedIn and implemented the code to clear all fields, setting all fields to null i.e.
private void ClearPropertiesOfItem(SPListItem itemCopiedOrCheckedIn, List<String> fieldsTobeCleared)
{
String validationFormula = "";
try
{
if (fieldsTobeCleared.Count > 0)
{
foreach (String fieldToBeCleared in fieldsTobeCleared)
{
foreach (SPField field in itemCopiedOrCheckedIn.Fields)
{
if (field.Title.Equals(fieldToBeCleared))
{
if (!String.IsNullOrEmpty(field.ValidationFormula))
{
validationFormula = field.ValidationFormula;
field.ValidationFormula = string.Empty;
field.Update();
}
itemCopiedOrCheckedIn[field.Id] = null;
if (!String.IsNullOrEmpty(validationFormula))
{
field.ValidationFormula = validationFormula;
field.Update();
}
}
}
}
itemCopiedOrCheckedIn.SystemUpdate();
}
}
catch (Exception Ex)
{
throw new Exception(base.GetResourceString(COMMON.Constants.EXCEPTION_OCCURED_WHILE_CLEARING_PROPERTIES), Ex);
}
}
This worked well for all fields except the managed metadata or the taxonomy columns which give an exception while setting the value to null.
In order to clear these columns , we explicitly need to set the properties "WssId, TermGuid and Label" to null as is shown below:
private void ClearPropertiesOfItem(SPListItem itemCopiedOrCheckedIn, List<String> fieldsTobeCleared)
{
String validationFormula = "";
try
{
if (fieldsTobeCleared.Count > 0)
{
foreach (String fieldToBeCleared in fieldsTobeCleared)
{
foreach (SPField field in itemCopiedOrCheckedIn.Fields)
{
if (field.Title.Equals(fieldToBeCleared))
{
if (!String.IsNullOrEmpty(field.ValidationFormula))
{
validationFormula = field.ValidationFormula;
field.ValidationFormula = string.Empty;
field.Update();
}
//special handling for managed metadata column (single value)
if (field.TypeAsString.Equals(“TaxonomyFieldType
“))
{
if (itemCopiedOrCheckedIn[field.Id] != null)
{
TaxonomyFieldValue managedMetadataFieldValue = itemCopiedOrCheckedIn[field.Id] as TaxonomyFieldValue;
managedMetadataFieldValue.WssId = 0;
managedMetadataFieldValue.TermGuid = null;
managedMetadataFieldValue.Label = null;
TaxonomyField managedMetadataField = itemCopiedOrCheckedIn.Fields[field.Id] as TaxonomyField;
managedMetadataField.SetFieldValue(itemCopiedOrCheckedIn, managedMetadataFieldValue);
}
}
else if (field.TypeAsString.Equals("TaxonomyFieldTypeMulti"))//special handling for managed metadata column (multi value)
{
if (itemCopiedOrCheckedIn[field.Id] != null)
{
TaxonomyFieldValueCollection managedMetadataFieldValueColl = new TaxonomyFieldValueCollection(string.Empty);
managedMetadataFieldValueColl.PopulateFromLabelGuidPairs(itemCopiedOrCheckedIn[field.Id].ToString());
int fieldValueCount = managedMetadataFieldValueColl.Count;
managedMetadataFieldValueColl.RemoveRange(0, fieldValueCount);
TaxonomyField managedMetadataField = itemCopiedOrCheckedIn.Fields[field.Id] as TaxonomyField;
managedMetadataField.SetFieldValue(itemCopiedOrCheckedIn, managedMetadataFieldValueColl);
}
}
else
{
itemCopiedOrCheckedIn[field.Id] = null;
}
if (!String.IsNullOrEmpty(validationFormula))
{
field.ValidationFormula = validationFormula;
field.Update();
}
}
}
}
itemCopiedOrCheckedIn.SystemUpdate();
}
}
catch (Exception Ex)
{
throw new Exception(base.GetResourceString(COMMON.Constants.EXCEPTION_OCCURED_WHILE_CLEARING_PROPERTIES), Ex);
}
}
