When creating your own configuration section it's not possible to enforce a specific length for a specific property.

Eg:

   1:      public class CryptoSection : ConfigurationSection   2:      {   3:          #region Construction   4:      5:          public CryptoSection()   6:          {   7:          }   8:      9:          #endregion  10:     11:          #region Properties  12:     13:          [ConfigurationProperty("decryptionKey", IsRequired = true, IsKey = false)]  14:          [StringValidator(MinLength = 24, MaxLength = 24)]  15:          public string DecryptionKey  16:          {  17:              get  18:              {  19:                  return (string) this["decryptionKey"];  20:              }  21:              set  22:              {  23:                  this["decryptionKey"] = value;  24:              }  25:          }  26:     27:          #endregion  28:      }
Then calling the following lines will throw an exception because for some reason when the validator gets invoked the first time this["decryptionKey"] will always be "" and therefore a length of 0:

   1:          CryptoSection cs = ConfigurationManager.GetSection("cryptoSection") as CryptoSection;   2:          Response.Write("DecryptionKey = " + cs.DecryptionKey);
The exception being thrown is:

ArgumentException: The string must be at least 24 characters long.]
   System.Configuration.StringValidator.Validate(Object value) +247
   System.Configuration.ConfigurationProperty.Validate(Object value) +27

[ConfigurationErrorsException: The value for the property 'decryptionKey' is not valid. The error is: The string must be at least 24 characters long.]
   System.Configuration.BaseConfigurationRecord.CallCreateSection(Boolean inputIsTrusted, FactoryRecord factoryRecord, SectionRecord sectionRecord, Object parentConfig, ConfigXmlReader reader, String filename, Int32 line) +276
....


The only work-around i have found so far is by setting in the ConfigurationPropertyAttribute a default value with a length of 24 (Eg: 24 spaces), no need. There has to be a better way otherwise the the MinLength of the StringValidator is useless in this context because the value will always be a String.Empty when the validator is invoked.

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