Attribute 介紹

[DefaultValueAttribute(Int32.MinValue)]
public float minValue { get; set; }

System.Reflection.PropertyInfo[] listPropertyInfo = this.GetType().GetProperties();
foreach (System.Reflection.PropertyInfo propertyInfo in listPropertyInfo) {
    if (propertyInfo != null && propertyInfo.CanWrite) {
        AttributeCollection attribute = TypeDescriptor.GetProperties(this)[propertyInfo.Name].Attributes;
        DefaultValueAttribute myAttribute = (DefaultValueAttribute)attribute[typeof(DefaultValueAttribute)];
        if (myAttribute != null)
            propertyInfo.SetValue(this, myAttribute.Value, null);
    }
}

public float minValue { get; set; } = Int32.MinValue

class HelpAttribute : Attribute {
    public string HelpText { get; set; }
}

[AttributeUsage(AttributeTargets.Property)]
class Check : Attribute {
    public int MaxLength { get; set; }
}

// Loop through all properties
foreach (PropertyInfo p in objtype.GetProperties()) {
    // for every property loop through all attributes
    foreach (Attribute a in p.GetCustomAttributes(false)) {
        Check c = (Check)a;
        if (p.Name == "CustomerCode") {
            // Do the length check and and raise exception accordingly
            if (obj.CustomerCode.Length > c.MaxLength)
                throw new Exception(" Max length issues ");
        }
    }
}