This error showing the error number where the constructor declared example below

public List<string> ChangedProperties { get; set; }

       public bool ShouldDisable { get; set; }

       public BusinessRecipient()

       {

           ChangedProperties = new List<string>();

       }

I have tried the data annotation solution

[Required]

public List<string> ChangedProperties { get; set; }

       public bool ShouldDisable { get; set; }

       public BusinessRecipient()

       {

           ChangedProperties = new List<string>();

       }