diff --git a/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj b/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj
index d384531c..7c273885 100644
--- a/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj
+++ b/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj
@@ -11,6 +11,7 @@
     <Copyright>Copyright © HandyOrg 2018-2019</Copyright>
     <FileVersion>2.0.0.0</FileVersion>
     <AssemblyVersion>2.0.0.0</AssemblyVersion>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
     <DefineConstants>TRACE;Core</DefineConstants>
diff --git a/src/Core_30/HandyControl_Core_30/HandyControl_Core_30.csproj b/src/Core_30/HandyControl_Core_30/HandyControl_Core_30.csproj
index f5711c96..34c1ddeb 100644
--- a/src/Core_30/HandyControl_Core_30/HandyControl_Core_30.csproj
+++ b/src/Core_30/HandyControl_Core_30/HandyControl_Core_30.csproj
@@ -11,6 +11,7 @@
     <Copyright>Copyright © HandyOrg 2018-2019</Copyright>
     <Description>Contains some commonly used simple WPF controls</Description>
     <Configurations>Debug;Release</Configurations>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
     <DefineConstants>TRACE;Core</DefineConstants>
diff --git a/src/Net_40/HandyControlDemo_Net_40/HandyControlDemo_Net_40.csproj b/src/Net_40/HandyControlDemo_Net_40/HandyControlDemo_Net_40.csproj
index 82e5ee46..766280db 100644
--- a/src/Net_40/HandyControlDemo_Net_40/HandyControlDemo_Net_40.csproj
+++ b/src/Net_40/HandyControlDemo_Net_40/HandyControlDemo_Net_40.csproj
@@ -26,6 +26,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
diff --git a/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj b/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj
index b64921df..0cf73688 100644
--- a/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj
+++ b/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj
@@ -23,6 +23,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
diff --git a/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj b/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj
index 36a1fec2..58477f84 100644
--- a/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj
+++ b/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj
@@ -60,6 +60,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net45|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
diff --git a/src/Net_GE45/HandyControl_Net_GE45/HandyControl_Net_GE45.csproj b/src/Net_GE45/HandyControl_Net_GE45/HandyControl_Net_GE45.csproj
index a9df5f10..a3dbfe7e 100644
--- a/src/Net_GE45/HandyControl_Net_GE45/HandyControl_Net_GE45.csproj
+++ b/src/Net_GE45/HandyControl_Net_GE45/HandyControl_Net_GE45.csproj
@@ -58,6 +58,7 @@
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net45|AnyCPU' ">
     <DebugType>pdbonly</DebugType>