How to set RelationshipDeleteBehavior on a list using a site column and content type programatically CSOM c#

Question

On Prem development machine, I'm writng a deployment routine in c# using the client object model.  I've created some site columns of type Lookup, I've created a content type and added those lookup columns to it and I've created a list using the
content type.  I want to set the RelationshipDeleteBehavior property on some of the lookup columns in the list.  I'm also using the 16 assemblies.
List list = cc.Web.GetListByTitle("MyList");
cc.Load(list);
cc.ExecuteQuery();
Field f = list.Fields.GetByInternalNameOrTitle("MyLookupField");
cc.Load(f);
cc.ExecuteQuery();
(f
as
FieldLookup).RelationshipDeleteBehavior =
RelationshipDeleteBehaviorType.Restrict;
f is returning as a Field but (f
as
FieldLookup) is returning null here.  Any insight on this?
Thank you.
Dan Budimir

Answer 1

Hi,
We can use SP.ClientContext.castTo method to convert the field to lookup field . The following code snippet for your reference:
ClientContext context = new ClientContext("http://siteurl");
NetworkCredential credentials = new NetworkCredential("username", "password", "domain");
context.Credentials = credentials;
Web web = context.Web;
List list = web.Lists.GetByTitle("MyList");
Field field = list.Fields.GetByInternalNameOrTitle("MyLookupField");
FieldLookup lookupField = context.CastTo<FieldLookup>(field);
lookupField.RelationshipDeleteBehavior = RelationshipDeleteBehaviorType.Restrict;
lookupField.Indexed = true;
lookupField.Update();
context.ExecuteQuery();
Thanks,
Dennis Guo
TechNet Community Support
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Dennis Guo
TechNet Community Support