C# Extend Web Reference Class with Lost Attributes

Question

Is it possible, to replace lost attributes, by extending a class from a Web Reference.

For example, previously a class containing a property called 'Amount` was part of the same project as defined below:

public class Test
{
    [Required]
    [Display(Name = "Amount", Description = "Amount")]
    [DisplayFormat(DataFormatString = "{0:F2}", ApplyFormatInEditMode = true)]
    [Range(1000, int.MaxValue)]
    public decimal Amount { get; set; }
}

The class containing the property as written above was then moved to an external project and referenced as a Web Reference. The class imported has the property 'Amount' however is simply as below:

[System.CodeDom.Compiler.GeneratedCodeAttribute("System.Xml", "4.7.3190.0")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(Namespace="http://tempuri.org/")]
public partial class Test {

    private decimal amountField;

    /// <remarks/>
    public decimal Amount {
        get {
            return this.amountField;
        }
        set {
            this.amountField = value;
        }
    }
}

As you can see, attributes such as [Required], [Display(Name = "Amount", Description = "Amount")], [Display(Name = "Amount", Description = "Amount")], [DisplayFormat(DataFormatString = "{0:F2}", ApplyFormatInEditMode = true)] and [Range(1000, int.MaxValue)] have been obmitted.

These attributes are still required for Model Validation, how can I extend the imported class by adding the missing attributes, so that Form Validation is not affected?