diff --git a/ClosedXML/ClosedXML.csproj b/ClosedXML/ClosedXML.csproj
index b17bde2..2d8b034 100644
--- a/ClosedXML/ClosedXML.csproj
+++ b/ClosedXML/ClosedXML.csproj
@@ -26,6 +26,7 @@
     <WarningLevel>4</WarningLevel>
     <NoWarn>1591</NoWarn>
     <Prefer32Bit>false</Prefer32Bit>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
diff --git a/ClosedXML_Examples/ClosedXML_Examples.csproj b/ClosedXML_Examples/ClosedXML_Examples.csproj
index a870a50..b0bc2fb 100644
--- a/ClosedXML_Examples/ClosedXML_Examples.csproj
+++ b/ClosedXML_Examples/ClosedXML_Examples.csproj
@@ -25,6 +25,7 @@
     <PlatformTarget>AnyCPU</PlatformTarget>
     <ErrorReport>prompt</ErrorReport>
     <Prefer32Bit>false</Prefer32Bit>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|AnyCPU'">
     <OutputPath>bin\Release\</OutputPath>
diff --git a/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj b/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
index d72ca28..fa38f46 100644
--- a/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
+++ b/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
@@ -23,6 +23,7 @@
     <PlatformTarget>AnyCPU</PlatformTarget>
     <ErrorReport>prompt</ErrorReport>
     <Prefer32Bit>false</Prefer32Bit>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|AnyCPU'">
     <OutputPath>bin\Release\</OutputPath>
diff --git a/ClosedXML_Tests/ClosedXML_Tests.csproj b/ClosedXML_Tests/ClosedXML_Tests.csproj
index 08ec404..6e9bd05 100644
--- a/ClosedXML_Tests/ClosedXML_Tests.csproj
+++ b/ClosedXML_Tests/ClosedXML_Tests.csproj
@@ -26,6 +26,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <Prefer32Bit>false</Prefer32Bit>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>