How do I replace an entire array of subdocuments in MongoDB?

I think you have to do something like this:

var newArray = new BSONArray {
    new BSONDocument { { "text", "XYZ" }, { "url", "www.xyz.com" } },
    new BSONDocument { { "text", "efg" }, { "url", "www.efg.com" } },
    new BSONDocument { { "text", "ijk" }, { "url", "www.ijk.com" } }
};

var update = Update.Set( "links", newArray );

collection.Update( query, update );

Or whatever method you can to cast as a valid BSONValue.

So equivalent to shell:

{ "links" : [ { "text" : "abc" } ] }

> db.collection.update(
      {},
      { $set: 
          { links: [ 
              { text: "xyz", url: "something" },
              { text: "zzz", url: "else" }
          ]}
      })

>db.collection.find({},{ _id: 0, links:1 }).pretty()

{ "links" : [
            {
                    "text" : "xyz",
                    "url" : "something"
            },
            {
                    "text" : "zzz",
                    "url" : "else"
            }
    ]
}

So that works.

You clearly need something else other than embedded code. But hopefully that puts you on the right track.

I am here because I saw 5k views on this post, I'm adding some stuff may be it help other who looking for answer of above

 db.collectionName.insertOne({
      'links': [
                 {
                     "text" : "XYZ",
                      "url" : "www.xyz.com"
                  }
        ]
  });

now run this query which help to replace older data

db.collectionName.update(
      {
        _id: ObjectId("your object Id")
      }, 
      {
        $set: 
         {
          'links':[ {
                     "text" : "XYZ1",
                     "url" : "www.xyz.com1"
                   } ]
         }
      });