Complete the following code snippet to correctly configure Azure Cognitive Search in a chat application.

var options = new {{slot1}}();
Messages = {
    new ChatMessage(ChatRole.User, "What are the differences between Azure Machine Learning and Azure AI services?"),
},
AzureExtensionsOptions = new AzureChatExtensionsOptions()
{
    Extensions =
    {
        new {{slot2}}()
        {
            SearchEndpoint = new Uri(searchEndpoint),
            SearchKey = new AzureKeyCredential(searchKey),
            IndexName = searchIndex,
        }
    }
};