Button button = control as Button;
 
if (button != null) 
  ...
else 
  ...

match (control) {
  | button is Button => ...
  | listv is ListView => ...
  | _ => ... // null case
}

_providersSection = (ConfigurationManager.GetSection("SmallBusinessDataProviders")) as SmallBusinessDataProvidersSection;

S>_providersSection = (ConfigurationManager.GetSection("SmallBusinessDataProviders")) as SmallBusinessDataProvidersSection;
S>

S>Динамик тайпкаст ( :> ) не спас на этот раз. Что делать

_providersSection = match(ConfigurationManager.GetSection("SmallBusinessDataProviders")) {
   | section is SmallBusinessDataProvidersSection => section
   | _ => null
}

S>_providersSection = (ConfigurationManager.GetSection("SmallBusinessDataProviders")) as SmallBusinessDataProvidersSection;
S>

S>Динамик тайпкаст ( :> ) не спас на этот раз. Что делать

_providersSection = match(ConfigurationManager.GetSection("SmallBusinessDataProviders")) {
 | x is SmallBusinessDataProvidersSection => x
 | _ => null
}

match(some_variant) {
  | SomeVariant.A as a => WriteLine(a.i);
  | SomeVariant.B as b => WriteLine(b.x);
}

H>_providersSection = match(ConfigurationManager.GetSection("SmallBusinessDataProviders")) {
H> | x is SmallBusinessDataProvidersSection => x
H> | _ => null
H>}
H>

<section name="FlowWebDataProviders" type="FlowWebProvidersSection" requirePermission="false"/>

  <FlowWebDataProviders peopleProviderName="sqlProvider" IzmListProviderName="sqlProvider">
    <PeopleProviders>
      <add name="sqlProvider" type="SqlPeopleProvider" connectionStringName="FlowServerConnectionString"/>
      <add name="xmlProvider" type="XmlPeopleProvider" schemaFile="People.xsd" dataFile="People.xml"/>
    </PeopleProviders>
    <IzmListProviders>
      <add name="sqlProvider" type="SqlIzmListProvider" connectionStringName="FlowServerConnectionString"/>
    </IzmListProviders>
  </FlowWebDataProviders>

  public class FlowWebProvidersSection : ConfigurationSection
  {
    [ConfigurationProperty("peopleProviderName", IsRequired = true)]
    public PeopleProviderName : string
    {
        get { this["peopleProviderName"] :> string }
        set { this["peopleProviderName"] = value; }
    }
    [ConfigurationProperty("IzmListProviderName", IsRequired = true)]
    public IzmListProviderName : string
    {
        get { (this["IzmListProviderName"] :> string) }
        set { this["IzmListProviderName"] = value; }
    }
    [ConfigurationProperty("PeopleProviders")]
    [ConfigurationValidatorAttribute(typeof(ProviderSettingsValidation))]
    public PeopleProviders : ProviderSettingsCollection
    {
        get { this["PeopleProviders"] :> ProviderSettingsCollection }
    }
    [ConfigurationProperty("IzmListProviders")]
    [ConfigurationValidatorAttribute(typeof(ProviderSettingsValidation))]
    public IzmListProviders : ProviderSettingsCollection
    {
        get { this["IzmListProviders"] :> ProviderSettingsCollection }
    }
  }

public class ProviderSettingsValidation : ConfigurationValidatorBase
  {
    public override CanValidate(typex : Type) : bool
    {
         if(typex : object == typeof(ProviderSettingsCollection)) true else false
    }

    /// <summary>
    // validate the provider section    
    /// </summary>
    public override Validate(value : object) : void
    {
      mutable providerCollection : ProviderSettingsCollection = match(value) 
             {
                | x is ProviderSettingsCollection => x
                | _ => null
             }
      unless (providerCollection == null) 
      {
        foreach (_provider is ProviderSettings in providerCollection) 
        {
          when (String.IsNullOrEmpty(_provider.Type)) 
          {
            throw ConfigurationErrorsException("Type was not defined in the provider");
          }
          mutable dataAccessType : Type = Type.GetType(_provider.Type);
          when (dataAccessType == null) 
          {
              throw (InvalidOperationException("Provider's Type could not be found"));
          }
        }
      }
    }
  }

<section name="FlowWebDataProviders" type="MyProject.Namespace.FlowWebProvidersSection, MyProject.Assembly.Name" requirePermission="false" />

public class ProviderSettingsValidation : ConfigurationValidatorBase
  {
    public override CanValidate(typex : Type) : bool
    {
         typeof(ProviderSettingsCollection).Equals(typex)
    }

    /// <summary>
    // validate the provider section    
    /// </summary>
    public override Validate(value : object) : void
    {
        | providerCollection is ProviderSettingsCollection =>
            foreach (_provider is ProviderSettings in providerCollection) 
            {
              when (String.IsNullOrEmpty(_provider.Type)) 
                throw ConfigurationErrorsException("Type was not defined in the provider");

              def dataAccessType = Type.GetType(_provider.Type);
              when (null == dataAccessType) 
                throw ConfigurationErrorsException("Provider's Type could not be found");
            }        
        | _ => ();
    }
  }

<section name="myConfigSection" type="MyProject.MyConfigSection, MyProject" />

H><section name="myConfigSection" type="MyProject.MyConfigSection, MyProject" />
H>

namespace Flow_WEB_Nemerle.Config
{
  public class FlowWebProvidersSection : ConfigurationSection

<section name="FlowWebDataProviders" type="Flow_WEB_Nemerle.Config.FlowWebProvidersSection, Flow WEB Nemerle" requirePermission="false" allowDefinition="MachineToApplication"/>

<section name="FlowWebDataProviders" type="Flow_WEB_Nemerle.Config.FlowWebProvidersSection, Flow_WEB_Nemerle" requirePermission="false" allowDefinition="MachineToApplication"/>

              def dataAccessType = Type.GetType(_provider.Type);
              when (null == dataAccessType) 
                throw ConfigurationErrorsException("Provider's Type could not be found");

S>              def dataAccessType = Type.GetType(_provider.Type);
S>              when (null == dataAccessType) 
S>                throw ConfigurationErrorsException("Provider's Type could not be found");
S>

<add name="sqlProvider" type="SqlPeopleProvider" connectionStringName="FlowServerConnectionString"/>