diff --git a/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj b/src/Core_30/HandyControlDemo_Core_30/HandyControlDemo_Core30.csproj
index 9b292a8c..5cccbbe1 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>2.2.0.0</FileVersion>
     <AssemblyVersion>2.2.0.0</AssemblyVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>8.0</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 f5884ac0..cbf01071 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>8.0</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 272f80dc..e93ae8aa 100644
--- a/src/Net_40/HandyControlDemo_Net_40/HandyControlDemo_Net_40.csproj
+++ b/src/Net_40/HandyControlDemo_Net_40/HandyControlDemo_Net_40.csproj
@@ -26,7 +26,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -37,6 +37,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup>
     <ApplicationIcon>..\..\Shared\HandyControlDemo_Shared\Resources\Img\icon.ico</ApplicationIcon>
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 2ee68fd7..28017834 100644
--- a/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj
+++ b/src/Net_40/HandyControl_Net_40/HandyControl_Net_40.csproj
@@ -23,7 +23,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -34,6 +34,7 @@
     <WarningLevel>4</WarningLevel>
     <DocumentationFile>bin\Release\HandyControl.xml</DocumentationFile>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="..\..\Shared\HandyControl_Shared\Properties\AssemblyInfo.cs">
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 be876603..ecf1a247 100644
--- a/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj
+++ b/src/Net_GE45/HandyControlDemo_Net_GE45/HandyControlDemo_Net_GE45.csproj
@@ -27,6 +27,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug-Net462|AnyCPU'">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -38,6 +39,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.6.2</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug-Net47|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -49,6 +51,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.7</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug-Net48|AnyCPU'">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -60,7 +63,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net45|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -71,6 +74,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net462|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -81,6 +85,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.6.2</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net47|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -91,6 +96,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.7</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release-Net48|AnyCPU'">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -101,6 +107,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup>
     <ApplicationIcon>..\..\Shared\HandyControlDemo_Shared\Resources\Img\icon.ico</ApplicationIcon>
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 7eb8f057..49bc677b 100644
--- a/src/Net_GE45/HandyControl_Net_GE45/HandyControl_Net_GE45.csproj
+++ b/src/Net_GE45/HandyControl_Net_GE45/HandyControl_Net_GE45.csproj
@@ -25,6 +25,7 @@
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug-Net462|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -36,6 +37,7 @@
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.6.2</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug-Net47|AnyCPU'">
     <DebugSymbols>true</DebugSymbols>
@@ -47,6 +49,7 @@
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.7</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug-Net48|AnyCPU'">
     <DebugSymbols>true</DebugSymbols>
@@ -58,7 +61,7 @@
     <WarningLevel>4</WarningLevel>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net45|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -70,6 +73,7 @@
     <DocumentationFile>bin\Release\HandyControl.xml</DocumentationFile>
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net462|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -81,6 +85,7 @@
     <DocumentationFile>bin\Release\HandyControl.xml</DocumentationFile>
     <TargetFrameworkVersion>v4.6.2</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release-Net47|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -92,6 +97,7 @@
     <DocumentationFile>bin\Release\HandyControl.xml</DocumentationFile>
     <TargetFrameworkVersion>v4.7</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release-Net48|AnyCPU'">
     <DebugType>pdbonly</DebugType>
@@ -103,6 +109,7 @@
     <DocumentationFile>bin\Release\HandyControl.xml</DocumentationFile>
     <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
     <netVersion>netgt40</netVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="..\..\Shared\HandyControl_Shared\Properties\AssemblyInfo.cs">