ConfigurationValidatorAttribute Class

Definition

Namespace:

System.Configuration

Assembly:

System.Configuration.ConfigurationManager.dll

Source:

ConfigurationValidatorAttribute.cs

Serves as the base class for the System.Configuration validator attribute types.

C#

[System.AttributeUsage(System.AttributeTargets.Property)]
public class ConfigurationValidatorAttribute : Attribute

Inheritance

Object

Attribute

ConfigurationValidatorAttribute

Derived

System.Configuration.CallbackValidatorAttribute

System.Configuration.IntegerValidatorAttribute

System.Configuration.LongValidatorAttribute

System.Configuration.PositiveTimeSpanValidatorAttribute

System.Configuration.RegexStringValidatorAttribute

System.Configuration.StringValidatorAttribute

System.Configuration.SubclassTypeValidatorAttribute

System.Configuration.TimeSpanValidatorAttribute

Attributes

AttributeUsageAttribute

Examples

The following code examples demonstrate how to create two custom validators using the ConfigurationValidatorAttribute type. The first example performs validation using hard-coded parameters; the second example performs validation using the parameters assigned to it at the time it is applied to the related section property. This code example also contains three supporting files. The first file contains the custom section that uses the validators described above, the second file contains a custom converter type, and the third file contains the console application that builds and uses the custom validators and the section that contains them.

The following code example shows how to create a fixed validator with hard-coded parameters.

C#

using System;
using System.Collections.Generic;
using System.Collections;
using System.Text;
using System.Configuration;

namespace Samples.AspNet
{
    // Show how to create a custom fixed 
    // validator. That is a validator whose
    // validation parameters are hard code in this
    // type.
    public class FixedValidator :
            ConfigurationValidatorBase
    {
       
        public override bool CanValidate(Type type)
        {
            return type == typeof(Automobile);
        }

        public override void Validate(object value)
        {

            ArrayList make = new ArrayList();

            make.Add("Ferrari");
            make.Add("Porsche");
            make.Add("Lamborghini");

            int minYear = 2004;
            long maxMiles = 100;
            string color = "red";
            
            Automobile car = (Automobile)value;

            try
            {
                if (!make.Contains(car.Make))
                {
                    throw new ConfigurationErrorsException(
                       "My dream car is not made by " + car.Make);
                }

                // Make sure the year is valid 
                if (car.Year < minYear)
                {

                    throw new ConfigurationErrorsException(
                       "My dream car cannot be older than " + minYear.ToString());
                }

                // Make sure the car can still run on its own
                if (car.Miles > maxMiles)
                {
                  throw new ConfigurationErrorsException(
                        "My dream car drive odometer cannot read more than " + 
                        maxMiles.ToString() + " miles");
                }

                // Validate color
                if (car.Color.ToLower() != color)
                {
                    throw new ConfigurationErrorsException(
                        "My dream car can oly be " + color);
                }
            }
            catch (ConfigurationErrorsException err)
            {
                Console.WriteLine(err.ToString());
            }
        }
    }
  }

The following code example shows how to create a programmable validator.

C#

using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;

namespace Samples.AspNet
{

    // Show how to create a custom programmable 
    // validator. That is a validator whose
    // validation parameters can be passed when the
    // validator is applied to a property.
    public class ProgrammableValidator : 
        ConfigurationValidatorBase
    {
        private string pmake;
        private string pcolor;
        private long pmaxMiles;
        private int pminYear;

        public ProgrammableValidator(string make, string color, 
            long maxMiles, int minYear)
        {
            pmake = make;
            pcolor = color;
            pminYear = minYear;
            pmaxMiles = maxMiles;
        }

        public override bool CanValidate(Type type)
        {
            return type == typeof(Automobile);
        }

        public override void Validate(object value)
        {

            Automobile car = (Automobile)value;

            try
            {

                // Validate make
                if (car.Make != pmake)
                {
                    throw new ConfigurationErrorsException(
                       "I do not by cars made by " + car.Make);
                }

                // Validate color
                if (car.Color != pcolor)
                {
                    throw new ConfigurationErrorsException(
                        "My commute car must be " + pcolor);
                }

                // Validate year
                if (car.Year < pminYear)
                {
                    throw new ConfigurationErrorsException(
                        "It's about time you get a new car.");
                }

                // Validate miles
                if (car.Miles > pmaxMiles)
                {
                    throw new ConfigurationErrorsException(
                        "Don't take too long trips with that car.");
                }
            }
            catch (ConfigurationErrorsException err)
            {
                Console.WriteLine(err.ToString());
            }
        }
    }

    public class ProgrammableValidatorAttribute : 
        ConfigurationValidatorAttribute
    {
        private string pmake;
        private string pcolor;
        private int pminYear;
        private long pmaxMiles;

        public string Make
        {
            get { return pmake; }
            set { pmake = value; }
        }

        public string Color
        {
            get { return pcolor; }
            set { pcolor = value; }
        }

        public int MinYear
        {
            get { return pminYear; }
            set { pminYear = value; }
        }
        public long MaxMiles
        {
            get { return pmaxMiles; }
            set { pmaxMiles = value; }
        }

        public ProgrammableValidatorAttribute(string make, string color,
            long miles, int year)
        {
            pmake = make;
            pcolor = color;
            pminYear = year;
            pmaxMiles = miles;
        }

        public override ConfigurationValidatorBase ValidatorInstance
        {
            get
            {
                return new ProgrammableValidator(pmake, pcolor, pmaxMiles, pminYear);
            }
        }
    }
}

The following code example shows how to create a custom section using the previous validators.

C#

using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.ComponentModel;
using System.Globalization;

namespace Samples.AspNet
{
    // Define the distinctive 
    // charecteristics of a car.
    public sealed class Automobile
    {
        public enum specification
        {
            make=0, color=1, miles=2, year=3, picture=4
        };

        public string Make;
        public string Color;
        public int Year;
        public long Miles;
        public string Picture;
    }

    // Define a custom section to select a car.
    // This section contains two properties one
    // to define a commute car the other 
    // to define a dream car.
    // This generates a configuration section such as:
    // <Cars commute="Make:AlfaRomeo Color:Blue Miles:10000 Year:2002"
    // dream="Make:Ferrari Color:Red Miles:10 Year:2005" />
    public sealed class SelectCar :
        ConfigurationSection
    {
        // Define your commute car.
        // The ProgrammableValidatorAttribute allows you to define the 
        // chracteristics of your commute car by changing
        // the values you pass to the next.
        // See the ProgrammableValidatorAttribute for details.
        [ProgrammableValidator("AlfaRomeo", "Blue", 10000, 2002)]
        
        // The AutomobileConverter converts between the Automobile
        // object and its related configuration commute attribute 
        // string value. 
        // Refer to AutomobileConverter for details.
        [TypeConverter(typeof(AutomobileConverter))]
        
        // Define the name of the configuration attribute to associate
        // with this property. Enter the default values.
        // Remember these default values must reflect the parameters
        // you entered in the ProgrammableValidator above.
        [ConfigurationProperty("commute", DefaultValue = "Make:AlfaRomeo Color:Blue Miles:10000 Year:2002")]
        public Automobile Commute
        {
            get
            {
                return (Automobile)this["commute"];
            }
            set
            {
                this["commute"] = value;
            }
        }

        // Apply the FixedValidatorAttribute. Here your choice 
        // (dream) is predetermined by the values contained in the
        // FixedValidatorAttribute. Being a dream, you would think 
        // otherwise but that's not the case.
        // See the FixedValidatorAttribute to choose your dream.
         [ConfigurationValidatorAttribute(
          typeof(FixedValidator))]

        // The AutomobileConverter converts between the Automobile
        // object and its related configuration dream attribute 
        // string value. 
        // Refer to AutomobileConverter for details.
        [TypeConverter(typeof(AutomobileConverter))]
        
        [ConfigurationProperty("dream", DefaultValue = "Make:Ferrari Color:Red Miles:10 Year:2005")]
        public Automobile Dream
        {
            get
            {
                return (Automobile)this["dream"];
            }
            set
            {
                this["dream"] = value;
            }
        }

        public SelectCar()
        {
            // Here you put your 
            // initializations, if necessary.
        }
    }    
}

The following code example shows how to create a custom converter.

C#

using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.ComponentModel;
using System.Globalization;

namespace Samples.AspNet
{
    // The AutomobileConverter converts between the Automobile
    // object and its related configuration commute and
    // dream attribute string values. 
    public sealed class AutomobileConverter :
    ConfigurationConverterBase
    {
       
        internal bool ValidateType(object value,
            Type expected)
        {
            bool result;

            if ((value != null) &&
                (value.GetType() != expected))
                result = false;
            else
                result = true;

            return result;
        }

        public override bool CanConvertTo(
            ITypeDescriptorContext ctx, Type type)
        {
            return (type == typeof(Automobile));
        }

        public override bool CanConvertFrom(
            ITypeDescriptorContext ctx, Type type)
        {
            return (type == typeof(Automobile));
        }

        public override object ConvertTo(
            ITypeDescriptorContext ctx, CultureInfo ci,
            object value, Type type)
        {
            string data;

            if (ValidateType(value, typeof(Automobile)))
            {
                string make = (string)(((Automobile)value).Make);
                string color = (string)(((Automobile)value).Color);
                string miles = (string)(((Automobile)value).Miles.ToString());
                string year = (string)(((Automobile)value).Year.ToString());

                data = "Make:" + make + " Color:" + color + 
                        " Miles:" + miles + " Year:" + year;
            }
            else
            {
                data = "Invalid type";
            }

            return data;
        }

        public override object ConvertFrom(
            ITypeDescriptorContext ctx, CultureInfo ci, object data)
        {
            Automobile selectedCar = 
                new Automobile();
 
            string carInfo  = (string)data;

            string[] carSpecs = carInfo.Split(new Char[] { ' ' });

            // selectedCar.Make = carSpecs[0].ToString();
            // selectedCar.Make = carSpecs[0].ToString();

            string make = 
                carSpecs[(int)Automobile.specification.make].ToString();
            string color =
                carSpecs[(int)Automobile.specification.color].ToString();
            string miles =
                carSpecs[(int)Automobile.specification.miles].ToString();
            string year =
                carSpecs[(int)Automobile.specification.year].ToString();

            selectedCar.Make = 
                make.Substring(make.IndexOf(":")+1);
            selectedCar.Color = 
                color.Substring(color.IndexOf(":") + 1);
            selectedCar.Miles = 
                Convert.ToInt32(miles.Substring(miles.IndexOf(":") + 1));
            selectedCar.Year = 
                Convert.ToInt32(year.Substring(year.IndexOf(":") + 1));
            
            return selectedCar;
        }
    }
}

The following code example shows how to create the console application that builds and uses the custom validators and their containing section.

C#

using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;

namespace Samples.AspNet
{

    class TestingConfigValidatorAttribute
    {
        static TestingConfigValidatorAttribute()
        {
            try
            {

                SelectCar car;

                // Get the current configuration file.
                System.Configuration.Configuration config =
                    ConfigurationManager.OpenExeConfiguration(
                    ConfigurationUserLevel.None);

                // Create the section entry for the selected car.
                if (config.Sections["Cars"] == null)
                {
                    
                    car = new SelectCar();
                    
                    config.Sections.Add("Cars", car);
                    
                    car.SectionInformation.ForceSave = true;
                    config.Save(ConfigurationSaveMode.Full);
                }
            }
            catch (ConfigurationErrorsException err)
            {
                Console.WriteLine(err.ToString());
            }
        }

        private static void GetCars()
        {

            try
            {
                // Get the current configuration file.
                System.Configuration.Configuration config =
                    ConfigurationManager.OpenExeConfiguration(
                    ConfigurationUserLevel.None);

                // Get the Cars section.
                SelectCar cars =
                    config.GetSection("Cars") as SelectCar;

                Console.WriteLine("Dream Make: {0} Color: {1} Miles: {2} Year: {3}",
                    cars.Dream.Make, cars.Dream.Color,
                    cars.Dream.Miles, cars.Dream.Year);

                Console.WriteLine("Commute Make: {0} Color: {1} Miles: {2} Year: {3}",
                    cars.Commute.Make, cars.Commute.Color,
                    cars.Commute.Miles, cars.Commute.Year);
            }
            catch (ConfigurationErrorsException err)
            {
                Console.WriteLine(err.ToString());
            }
        }

        private static void NotAllowedCars()
        {

            try
            {
                // Get the current configuration file.
                System.Configuration.Configuration config =
                    ConfigurationManager.OpenExeConfiguration(
                    ConfigurationUserLevel.None);

                Automobile dreamCar = new Automobile();
                dreamCar.Color = "Red";
                dreamCar.Make = "BMW";
                dreamCar.Miles = 10;
                dreamCar.Year = 2005;

                Automobile commuteCar = new Automobile();
                commuteCar.Color = "Blue";
                commuteCar.Make = "Yugo";
                commuteCar.Miles = 10;
                commuteCar.Year = 1990;

                // Get the Cars section.
                SelectCar cars =
                    config.GetSection("Cars") as SelectCar;

                cars.Dream = dreamCar;
                cars.Commute = commuteCar;
            }
            catch (ConfigurationErrorsException err)
            {
                Console.WriteLine(err.ToString());
            }
        }

        static void Main(string[] args)
        {
            GetCars();
            NotAllowedCars();
        }
    }
}

The following code example is a configuration excerpt used by the previous example.

XML

<?xml version="1.0" encoding="utf-8"?>  
<configuration>  
    <configSections>  
        <section name="Cars" type="Samples.AspNet.SelectCar, ConfigValidatorAttribute, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" allowLocation="false" allowDefinition="Everywhere" allowExeDefinition="MachineToApplication" restartOnExternalChanges="true" requirePermission="true" />  
    </configSections>  
    <Cars commute="Make:AlfaRomeo Color:Blue Miles:10000 Year:2002"  
        dream="Make:Ferrari Color:Red Miles:10 Year:2005" />  
</configuration>  

Remarks

All the ASP.NET configuration standard validator attribute types derive from ConfigurationValidatorAttribute. You can use this type to create your own custom validator attribute.

Constructors

ConfigurationValidatorAttribute()	Initializes a new instance of the ConfigurationValidatorAttribute class.
ConfigurationValidatorAttribute(Type)	Initializes a new instance of the ConfigurationValidatorAttribute class using the specified validator type.

Properties

ValidatorInstance	Gets the validator attribute instance.
ValidatorType	Gets the type of the validator attribute.

Applies to

See also

• IntegerValidatorAttribute
• TimeSpanValidatorAttribute
• StringValidatorAttribute