Added GetStatus() call.

samples/NetCoreConsole/NetCoreConsole.csproj

@@ -4,6 +4,7 @@
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp2.1</TargetFramework>
     <RootNamespace>ConsoleApp</RootNamespace>
+    <LangVersion>7.1</LangVersion>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">

samples/NetFXConsole/NetFXConsole.csproj

@@ -21,6 +21,7 @@
     <DefineConstants>DEBUG;TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <LangVersion>7.1</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -30,6 +31,7 @@
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <LangVersion>7.1</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />

src/NTwain/DataSource.cs

@@ -35,6 +35,17 @@ namespace NTwain
         public ReturnCode Close() => Session.DGControl.Identity.CloseDS(Identity);
 
 
+        /// <summary>
+        /// Gets the source status. Useful after getting a non-success return code.
+        /// </summary>
+        /// <returns></returns>
+        public TW_STATUS GetStatus()
+        {
+            TW_STATUS stat = default;
+            var rc = Session.DGControl.Status.GetSourceStatus(ref stat);
+            return stat;
+        }
+
 
         /// <summary>
         /// Returns a <see cref="System.String"/> that represents this instance.

src/NTwain/NTwain.csproj

@@ -19,6 +19,7 @@
     <AssemblyVersion>4.0.0.0</AssemblyVersion>
     <FileVersion>4.0.0.0</FileVersion>
     <Version>4.0.0</Version>
+    <LangVersion>7.1</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

src/NTwain/Triplets/DGControl.Status.cs

@@ -0,0 +1,22 @@
+using NTwain.Data;
+using NTwain.Internals;
+
+namespace NTwain.Triplets
+{
+    sealed class Status : BaseTriplet
+    {
+        internal Status(TwainSession session) : base(session) { }
+
+        public ReturnCode GetManagerStatus(ref TW_STATUS status)
+        {
+            return NativeMethods.DsmWin32(Session.Config.AppWin32, null,
+                DataGroups.Control, DataArgumentType.Status, Message.Get, ref status);
+        }
+
+        public ReturnCode GetSourceStatus(ref TW_STATUS status)
+        {
+            return NativeMethods.DsmWin32(Session.Config.AppWin32, Session.CurrentSource.Identity,
+                DataGroups.Control, DataArgumentType.Status, Message.Get, ref status);
+        }
+    }
+}

src/NTwain/Triplets/DGControl.cs

@@ -27,5 +27,8 @@ namespace NTwain.Triplets
 
         Callback2 _callback2;
         internal Callback2 Callback2 => _callback2 ?? (_callback2 = new Callback2(Session));
+
+        Status _status;
+        internal Status Status => _status ?? (_status = new Status(Session));
     }
 }

src/NTwain/TwainSession.cs

@@ -82,6 +82,17 @@ namespace NTwain
             return rc;
         }
 
+        /// <summary>
+        /// Gets the manager status. Useful after getting a non-success return code.
+        /// </summary>
+        /// <returns></returns>
+        public TW_STATUS GetStatus()
+        {
+            TW_STATUS stat = default;
+            var rc = DGControl.Status.GetManagerStatus(ref stat);
+            return stat;
+        }
+
         internal void RegisterCallback()
         {
             var callbackPtr = Marshal.GetFunctionPointerForDelegate(_callbackDelegate);
@@ -92,7 +103,8 @@ namespace NTwain
             if (rc == ReturnCode.Success) Debug.WriteLine("Registed Callback2 success.");
             else
             {
-
+                var status = GetStatus();
+                Debug.WriteLine($"Register Callback2 failed with condition code: {status.ConditionCode}.");
             }
 
 
@@ -106,7 +118,8 @@ namespace NTwain
                 if (rc == ReturnCode.Success) Debug.WriteLine("Registed Callback success.");
                 else
                 {
-
+                    var status = GetStatus();
+                    Debug.WriteLine($"Register Callback failed with {status.ConditionCode}.");
                 }
             }
         }