What is the assembly reference for Attribute class

Question

Hi,

 

I am trying to insert this class in my html helper but seem to be missing an assembly reference. Can you pls advice?here is my code im trying to insert into html helper:

 

[AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]

public class AtLeastOnePropertyAttribute : ValidationAttribute

{

private string[] PropertyList { get; set; }

public AtLeastOnePropertyAttribute(params string[] propertyList)

{

this.PropertyList = propertyList;

}

//See http://stackoverflow.com/a/1365669

public override object TypeId

{

get

{

return this;

}

}

public override bool IsValid(object value)

{

PropertyInfo propertyInfo;

foreach (string propertyName in PropertyList)

{

propertyInfo = value.GetType().GetProperty(propertyName);

if (propertyInfo != null && propertyInfo.GetValue(value, null) != null)

{

return true;

}

}

return false;

}

}