public class ValidateAtLeastOneChecked : ValidationAttribute {
    public string[] CheckBoxFields {get; set;}
    public ValidateAtLeastOneChecked(string[] checkBoxFields) {
        CheckBoxFields = checkBoxFields;
    }

    protected override ValidationResult IsValid(Object value, ValidationContext context) {
        Object instance = context.ObjectInstance;
        Type type = instance.GetType();

        foreach(string s in CheckBoxFields) {
            Object propertyValue = type.GetProperty(s).GetValue(instance, null);
            if (bool.Parse(propertyValue.ToString())) {
                return ValidationResult.Success;
            }
        }
        return new ValidationResult(base.ErrorMessageString);
    }
}

[ValidateAtLeastOneChecked(new string[] { "Checkbox1", "Checkbox2", "Checkbox3", "Checkbox4" }, ErrorMessageResourceType=typeof(ErrorMessageResources),ErrorMessageResourceName="SelectAtLeastOneTopic")]
public bool Checkbox1{ get; set; }
public bool Checkbox2{ get; set; }
public bool Checkbox3{ get; set; }
public bool Checkbox4{ get; set; }

public class ValidateAtLeastOneCheckedAttribute : ValidationAttribute
{
   protected override ValidationResult IsValid(object value, ValidationContext validationContext)
   {
      Type type = value.GetType();
      IEnumerable<PropertyInfo> checkBoxeProperties = type.GetProperties(BindingFlags.Instance | BindingFlags.Public).Where(p => p.PropertyType == typeof (bool));

      foreach (PropertyInfo checkBoxProperty in checkBoxeProperties)
      {
         var isChecked = (bool)checkBoxProperty.GetValue(value);
         if (isChecked)
         {
            return ValidationResult.Success;
         }
      }

      return new ValidationResult(base.ErrorMessageString);
   }
}

[ValidateAtLeastOneChecked]
public class CheckBoxList
{
   public bool Checkbox1 { get; set; }
   public bool Checkbox2 { get; set; }
   public bool Checkbox3 { get; set; }
   public bool Checkbox4 { get; set; }
   public bool Checkbox5 { get; set; }
}

Object propertyValue = type.GetProperty(s).GetValue(instance, null);
if (bool.Parse(propertyValue.ToString())) {//...