Example of "counter" entity written as a C# class

counter-entity-class.cs

public class CounterEntity
{
    [JsonProperty("value")]
    public int CurrentValue { get; set; }

    public void Add(int amount) => this.CurrentValue += amount;
    
    public void Reset() => this.CurrentValue = 0;
    
    public int Get() => this.CurrentValue;

    [FunctionName("Counter")]
    public static Task Run([EntityTrigger] IDurableEntityContext ctx) 
        => ctx.DispatchAsync<CounterEntity>();
}