Reflective implementation of ToString using customer attribute

There is one class as following:

public class OldDog
{
    public OldDog() { }

    public OldDog(string name, string host, string category)
    {
        this.name = name;
        this.host = host;
        this.category = category;
    }

    private string name;
    private string host;
    private string category;

    public string Name
    {
        get { return this.name; }
        set { this.name = value; }
    }

    public string Host
    {
        get { return this.host; }
        set { this.host = value; }
    }

    public string Category
    {
        get { return this.category; }
        set { this.category = value; }
    }

    public override string ToString()
    {
        StringBuilder result = new StringBuilder();

        result.Append("<OldDog>");
        result.Append("Name: " + Name);
        result.Append("Host: " + Host);
        result.Append("Category: " + Category);
        result.Append("</OldDog>");

        return result.ToString();
    }
}

After refactor

public class Dog
{
    public Dog() { }

    public Dog(string name, string host, string category)
    {
        this.name = name;
        this.host = host;
        this.category = category;
    }

    private string name;
    private string host;
    private string category;

    [IsOutputAttribute(true)]
    public string Name
    {
        get { return this.name; }
        set { this.name = value; }
    }

    [IsOutputAttribute(false)]
    public string Host
    {
        get { return this.host; }
        set { this.host = value; }
    }

    [IsOutputAttribute(true)]
    public string Category
    {
        get { return this.category; }
        set { this.category = value; }
    }

    public override string ToString()
    {
        StringBuilder result = new StringBuilder();
        PropertyInfo[] lst = this.GetType().GetProperties();

        int col = 0;
        foreach (PropertyInfo p in lst)
        {
            foreach (Attribute a in Attribute.GetCustomAttributes(p))
            {
                if (a.GetType() == typeof(IsOutputAttribute)
                    && ((IsOutputAttribute)a).IsOutput)
                {
                    if (col > 0)
                    {
                        result.Append("<br />");
                    }

                    result.Append(p.Name.ToString() +": " + p.GetValue(this, null));

                    col++;
                }
            }           
        }

        return result.ToString();
    }
}

public class IsOutputAttribute : Attribute
{ 
    protected bool isOutput;

    public bool IsOutput
    {
        get { return this.isOutput; }
        set { this.isOutput = value; }
    }

    public IsOutputAttribute(bool isOutput)
    {
        this.isOutput = isOutput;
    }
}

not enough, let's continue

public class Dog
{
    public Dog() { }

    public Dog(string name, string host, string category)
    {
        this.name = name;
        this.host = host;
        this.category = category;
    }

    private string name;
    private string host;
    private string category;

    [IsOutputAttribute(true)]
    public string Name
    {
        get { return this.name; }
        set { this.name = value; }
    }

    [IsOutputAttribute(false)]
    public string Host
    {
        get { return this.host; }
        set { this.host = value; }
    }

    [IsOutputAttribute(true)]
    public string Category
    {
        get { return this.category; }
        set { this.category = value; }
    }

    public override string ToString()
    {
        return SystemUtility.CustomerToString(this);
    }
}

public class IsOutputAttribute : Attribute
{ 
    protected bool isOutput;

    public bool IsOutput
    {
        get { return this.isOutput; }
        set { this.isOutput = value; }
    }

    public IsOutputAttribute(bool isOutput)
    {
        this.isOutput = isOutput;
    }
}

public static class SystemUtility
{
    public static string CustomerToString(Object obj)
    {

        StringBuilder result = new StringBuilder();
        PropertyInfo[] lst = obj.GetType().GetProperties();

        int col = 0;
        foreach (PropertyInfo p in lst)
        {
            foreach (Attribute a in Attribute.GetCustomAttributes(p))
            {
                if (a.GetType() == typeof(IsOutputAttribute)
                    && ((IsOutputAttribute)a).IsOutput)
                {
                    if (col > 0)
                    {
                        result.Append("<br />");
                    }

                    result.Append(p.Name.ToString() + ": " + p.GetValue(obj, null));

                    col++;
                }
            }
        }

        return result.ToString();
    }
}