c# - Unity: The type LogWriter cannot be constructed

Question

For the following "project" I am getting a very annoying and inexplicable error when resolving Unity for DI.

InvalidOperationException - The type LogWriter cannot be constructed. You must configure the container to supply this value.

?ex.Message; "Resolution of the dependency failed, type = "WindowsFormsApplication1.Performance", name = "(none)". Exception occurred while: while resolving. Exception is: InvalidOperationException - The type LogWriter cannot be constructed. You must configure the container to supply this value. ----------------------------------------------- At the time of the exception, the container was: Resolving WindowsFormsApplication1.Performance,(none) Resolving parameter "lw" of constructor WindowsFormsApplication1.Performance(Microsoft.Practices.EnterpriseLibrary.Logging.LogWriter lw, Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.ExceptionManager em) Resolving Microsoft.Practices.EnterpriseLibrary.Logging.LogWriter,(none) "

?ex.StackTrace; " at Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, Object existing, String name, IEnumerable1 resolverOverrides) in e:\Builds\Unity\UnityTemp\Compile\Unity\Unity\Src\UnityContainer.cs:line 515 at Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, String name, IEnumerable1 resolverOverrides) in e:BuildsUnityUnityTempCompileUnityUnitySrcUnityContainer.cs:line 485 at Microsoft.Practices.Unity.UnityContainer.Resolve(Type t, String name, ResolverOverride[] resolverOverrides) in e:BuildsUnityUnityTempCompileUnityUnitySrcUnityContainer.cs:line 173 at Microsoft.Practices.Unity.UnityContainerExtensions.Resolve[T](IUnityContainer container, ResolverOverride[] overrides) in e:BuildsUnityUnityTempCompileUnityUnitySrcUnityContainerExtensions.cs:line 504 at WindowsFormsApplication1.Form1.OnLoad(EventArgs e) in D:DevzoneTaskingWindowsFormsApplication1Form1.cs:line 33"

In a form:

  protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            try
            {
                IUnityContainer container = new UnityContainer();
                Performance p = container.Resolve<Performance>();
            }
            catch (Exception ex)
            {

            }
        }

Dependency class:

 public class Performance
    {
        public Performance(LogWriter lw, ExceptionManager em)
        {
        }
    }

Configuration File:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name="loggingConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.LoggingSettings, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true" />
        <section name="exceptionHandling" type="Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Configuration.ExceptionHandlingSettings, Microsoft.Practices.EnterpriseLibrary.ExceptionHandling, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true" />
    </configSections>
    <loggingConfiguration name="" tracingEnabled="true" defaultCategory="General">
        <listeners>
            <add name="Event Log Listener" type="Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners.FormattedEventLogTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
                listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.FormattedEventLogTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
                source="Enterprise Library Logging" formatter="Text Formatter"
                log="" machineName="." traceOutputOptions="None" />
        </listeners>
        <formatters>
            <add type="Microsoft.Practices.EnterpriseLibrary.Logging.Formatters.TextFormatter, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
                template="Timestamp: {timestamp}{newline}&#xA;Message: {message}{newline}&#xA;Category: {category}{newline}&#xA;Priority: {priority}{newline}&#xA;EventId: {eventid}{newline}&#xA;Severity: {severity}{newline}&#xA;Title:{title}{newline}&#xA;Machine: {localMachine}{newline}&#xA;App Domain: {localAppDomain}{newline}&#xA;ProcessId: {localProcessId}{newline}&#xA;Process Name: {localProcessName}{newline}&#xA;Thread Name: {threadName}{newline}&#xA;Win32 ThreadId:{win32ThreadId}{newline}&#xA;Extended Properties: {dictionary({key} - {value}{newline})}"
                name="Text Formatter" />
        </formatters>
        <categorySources>
            <add switchValue="All" name="General">
                <listeners>
                    <add name="Event Log Listener" />
                </listeners>
            </add>
            <add switchValue="All" name="Category2" />
        </categorySources>
        <specialSources>
            <allEvents switchValue="All" name="All Events" />
            <notProcessed switchValue="All" name="Unprocessed Category" />
            <errors switchValue="All" name="Logging Errors &amp; Warnings">
                <listeners>
                    <add name="Event Log Listener" />
                </listeners>
            </errors>
        </specialSources>
    </loggingConfiguration>
    <exceptionHandling>
        <exceptionPolicies>
            <add name="Policy">
                <exceptionTypes>
                    <add name="All Exceptions" type="System.Exception, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
                        postHandlingAction="NotifyRethrow" />
                </exceptionTypes>
            </add>
        </exceptionPolicies>
    </exceptionHandling>
</configuration>

Answer 1

You need to add the Enterprise Library extension to your container. Without it, the container doesn't read the config file and therefore doesn't know how to create Entlib objects, like the LogWriter.