c# nest elastic generic index create

Question

I have a generic "Create" method. This method will create index by generic type.

public void Create<T>(T node) 
{        
    if (!_elasticClient.IndexExists(_indexName).Exists)
    {
        var indexSettings = new IndexSettings();
        indexSettings.NumberOfReplicas = 1;
        indexSettings.NumberOfShards = 3;

        var createIndexDescriptor = new CreateIndexDescriptor(_indexName)
                .Mappings(ms => ms.Map<T>(m => m.AutoMap()))
                .InitializeUsing(new IndexState() { Settings = indexSettings })
                .Aliases(a => a.Alias(aliasName));

        var response = _elasticClient.CreateIndex(createIndexDescriptor);
    }

    _elasticClient.Index<T>(node, idx => idx.Index(_indexName));
}

But I getting errors:

1. The type 'T' must be a reference type in order to use it as parameter 'T' in the generic type or method 'MappingsDescriptor.Map(Func<TypeMappingDescriptor, ITypeMapping>)'

2. The type 'T' must be a reference type in order to use it as parameter 'T' in the generic type or method 'ElasticClient.Index(T, Func<IndexDescriptor, IIndexRequest>)'

Answer 1

The .Map<T>() method in nest uses a class constraint for T. You need to add the same class constraint to your generic T.

public void Create<T>(T node)
    where T: class
{
    // your code here
}