diff --git a/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj b/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj
index f9dad817..0d272ccf 100644
--- a/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj
+++ b/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj
@@ -11,7 +11,7 @@
     <Copyright>Copyright © HandyOrg 2018-2019</Copyright>
     <FileVersion>2.0.0.0</FileVersion>
     <AssemblyVersion>2.0.0.0</AssemblyVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>default</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 34c1ddeb..45ce9fb0 100644
--- a/src/Core_30/HandyControl_Core_30/HandyControl_Core_30.csproj
+++ b/src/Core_30/HandyControl_Core_30/HandyControl_Core_30.csproj
@@ -11,7 +11,7 @@
     <Copyright>Copyright © HandyOrg 2018-2019</Copyright>
     <Description>Contains some commonly used simple WPF controls</Description>
     <Configurations>Debug;Release</Configurations>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>default</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 105853a5..0dd1ca69 100644
--- a/src/Net_40/HandyControlDemo_Net_40/HandyControlDemo_Net_40.csproj
+++ b/src/Net_40/HandyControlDemo_Net_40/HandyControlDemo_Net_40.csproj
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="16.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
@@ -26,7 +26,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>default</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
diff --git a/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj b/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj
index 0cf73688..dccb1c9b 100644
--- a/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj
+++ b/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="16.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
     <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
@@ -23,7 +23,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>default</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
diff --git a/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj b/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj
index 049072a0..68202dc2 100644
--- a/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj
+++ b/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="16.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
@@ -60,7 +60,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>default</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 a3dbfe7e..fae23051 100644
--- a/src/Net_GE45/HandyControl_Net_GE45/HandyControl_Net_GE45.csproj
+++ b/src/Net_GE45/HandyControl_Net_GE45/HandyControl_Net_GE45.csproj
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="16.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
     <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
@@ -58,7 +58,7 @@
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>default</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net45|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
diff --git a/src/Shared/HandyControlDemo_Shared/HandyControlDemo_Shared.shproj b/src/Shared/HandyControlDemo_Shared/HandyControlDemo_Shared.shproj
index 9f82f523..554c16d2 100644
--- a/src/Shared/HandyControlDemo_Shared/HandyControlDemo_Shared.shproj
+++ b/src/Shared/HandyControlDemo_Shared/HandyControlDemo_Shared.shproj
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="16.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup Label="Globals">
     <ProjectGuid>c4694269-c9b8-45d5-87f8-d0088c532510</ProjectGuid>
     <MinimumVisualStudioVersion>14.0</MinimumVisualStudioVersion>
diff --git a/src/Shared/HandyControl_Shared/HandyControl_Shared.shproj b/src/Shared/HandyControl_Shared/HandyControl_Shared.shproj
index fb803c42..6fa3f1e8 100644
--- a/src/Shared/HandyControl_Shared/HandyControl_Shared.shproj
+++ b/src/Shared/HandyControl_Shared/HandyControl_Shared.shproj
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="16.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup Label="Globals">
     <ProjectGuid>aac11083-faca-405d-9197-5c1212d65656</ProjectGuid>
     <MinimumVisualStudioVersion>14.0</MinimumVisualStudioVersion>