/// <summary>
/// Creates an instance of the provider.
/// </summary>
/// <returns>
/// An instance of the provider or null if one could not be created.
/// </returns>
/// <exception cref="ProviderNotFoundException">
/// If an instance of the provider could not be created because the
/// type could not be found in the assembly.
/// </exception>
internal Provider.CmdletProvider CreateInstance()
{
// It doesn't really seem that using thread local storage to store an
// instance of the provider is really much of a performance gain and it
// still causes problems with the CmdletProviderContext when piping two
// commands together that use the same provider.
// get-child -filter a*.txt | get-content
// This pipeline causes problems when using a cached provider instance because
// the CmdletProviderContext gets changed when get-content gets called.
// When get-content finishes writing content from the first output of get-child
// get-child gets control back and writes out a FileInfo but the WriteObject
// from get-content gets used because the CmdletProviderContext is still from
// that cmdlet.
// Possible solutions are to not cache the provider instance, or to maintain
// a CmdletProviderContext stack in ProviderBase. Each method invocation pushes
// the current context and the last action of the method pops back to the
// previous context.
#if USE_TLS
// Next see if we already have an instance in thread local storage
object providerInstance = Thread.GetData(instance);
if (providerInstance == null)
{
#else
object providerInstance = null;
#endif
// Finally create an instance of the class
Exception invocationException = null;
try
{
providerInstance =
Activator.CreateInstance(this.ImplementingType);
}
catch (TargetInvocationException targetException)
{
invocationException = targetException.InnerException;
}
catch (MissingMethodException)
{
}
catch (MemberAccessException)
{
}
catch (ArgumentException)
{
}
#if USE_TLS
// cache the instance in thread local storage
Thread.SetData(instance, providerInstance);
}
#endif
if (providerInstance == null)
{
ProviderNotFoundException e = null;
if (invocationException != null)
{
e =
new ProviderNotFoundException(
this.Name,
SessionStateCategory.CmdletProvider,
"ProviderCtorException",
SessionStateStrings.ProviderCtorException,
invocationException.Message);
}
else
{
e =
new ProviderNotFoundException(
this.Name,
SessionStateCategory.CmdletProvider,
"ProviderNotFoundInAssembly",
SessionStateStrings.ProviderNotFoundInAssembly);
}
throw e;
}
Provider.CmdletProvider result = providerInstance as Provider.CmdletProvider;
Dbg.Diagnostics.Assert(
result != null,
"DiscoverProvider should verify that the class is derived from CmdletProvider so this is just validation of that");
result.SetProviderInformation(this);
return result;
}