Exclude property from being indexed

You should be able to set the OptOut value of the ElasticProperty attribute, like the following:

 [ElasticProperty(OptOut = true)]
 public string UnivId { get; set; }

In NEST 2.0 ElasticPropertyAttribute is replaced by per type attributes (StringAttribute, DateAttribute...). I used Ignore parameter to exclude property.

Exemple for string :

[String(Ignore = true)]
public string Id {get;set;}

If using Nest 5.0+, per the docs several ways to ignore a field:

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Ignore attribute should work:

using Nest;

[Ignore]
public string UnivId { get; set; }

JsonIgnore can also be used since Newtonsoft.Json is the default serializer used by Nest.

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Another way is to use type specific attribute mappings associated with the property. For example, since it's a string then use Text attribute:

[Text(Ignore = true)]
public string UnivId { get; set; }

or if an int use Number:

[Number(Ignore = true)]
public int Id { get; set; }

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In addition, instead of using an explicit attribute on the property, the mapping can be ignored using .DefaultMappingFor<... on ConnectionSettings (see docs for more detail)

var connectionSettings = new ConnectionSettings()
    .DefaultMappingFor<Type1>(m => m.Ignore(p => p.UnivId);

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However, if want to conditionally ignore an attribute if the value is null then use the following Newtonsoft.Json attribute with null handling setting:

[JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
public string UnivId { get; set; }

I found the above useful when doing partial updates on a doc but wanted to re-use the same C# class for indexing and avoid overwriting existing values in the index.