8.1 ConcurrencyMode and ETag

In OData V3 protocol, concurrencyMode is a special facet that can be applied to any primitive Entity Data Model (EDM) type. Possible values are None, which is the default, and Fixed. When used on an EntityType property, ConcurrencyMode specifies that the value of that declared property should be used for optimistic concurrency checks. In the metadata, concurrencyMode will be shown as following:

<EntityType Name="Order">
    <Key>
        <PropertyRef Name="Id" />
    </Key>
    <Property Name="Id" Type="Edm.Int32" Nullable="false" />
    <Property Name="ConcurrencyCheckRow" Type="Edm.String" Nullable="false" ConcurrencyMode="Fixed" /> />  
</EntityType>

There are two approaches to set concurrencyMode for a primitive property: Using ConcurrencyCheck attribute:

public class Order
{
    public int Id { get; set; }
    
    [ConcurrencyCheck]
    public string ConcurrencyCheckRow { get; set; }
}

Using API call

ODataModelBuilder builder = new ODataModelBuilder();
builder.Entity<Order>().Property(c => c.ConcurrencyCheckRow).IsConcurrencyToken;