Changing a single element of sharedMesh.uv

Hi, I am trying to change the Value of a single element of sharedMesh.uv . Replacing the whole Array works just fine.

So the following works:

 Vector2[] uvArray = new Vector2[n];
 
 TileMap.GetComponent<MeshFilter>().sharedMesh.uv = uvArray; 

However that replaces the whole sharedMesh.uv array when I really only need to update a small portion of it.

The following does not work (it gives not error but it just doesn't change the value)

 TileMap.GetComponent<MeshFilter>().sharedMesh.uv[0] = new Vector2(0.5f,0.25f);

Neither does

 TileMap.GetComponent<MeshFilter>().sharedMesh.uv[0].Set(0.5f,0.25f);

It's probably some very simple mistake I am making, would appreciate your help very much.