diff --git a/src/JT808.Protocol.Extensions.DependencyInjection/JT808.Protocol.Extensions.DependencyInjection.csproj b/src/JT808.Protocol.Extensions.DependencyInjection/JT808.Protocol.Extensions.DependencyInjection.csproj
index ca124b9..223b4d4 100644
--- a/src/JT808.Protocol.Extensions.DependencyInjection/JT808.Protocol.Extensions.DependencyInjection.csproj
+++ b/src/JT808.Protocol.Extensions.DependencyInjection/JT808.Protocol.Extensions.DependencyInjection.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netcoreapp2.2</TargetFramework>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>7.3</LangVersion>
     <Copyright>Copyright 2018.</Copyright>
     <Authors>SmallChi</Authors>
     <PackageId>JT808.Extensions.DependencyInjection</PackageId>
diff --git a/src/JT808.Protocol.Test/JT808.Protocol.Test.csproj b/src/JT808.Protocol.Test/JT808.Protocol.Test.csproj
index 86b7381..ab7050d 100644
--- a/src/JT808.Protocol.Test/JT808.Protocol.Test.csproj
+++ b/src/JT808.Protocol.Test/JT808.Protocol.Test.csproj
@@ -3,7 +3,7 @@
   <PropertyGroup>
     <TargetFramework>netcoreapp2.2</TargetFramework>
     <IsPackable>false</IsPackable>
-    <LangVersion>7.1</LangVersion>
+    <LangVersion>7.3</LangVersion>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
diff --git a/src/JT808.Protocol/JT808.Protocol.csproj b/src/JT808.Protocol/JT808.Protocol.csproj
index dc382fb..b44da2f 100644
--- a/src/JT808.Protocol/JT808.Protocol.csproj
+++ b/src/JT808.Protocol/JT808.Protocol.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
-    <LangVersion>8.0</LangVersion>
+    <LangVersion>7.3</LangVersion>
     <Copyright>Copyright 2018.</Copyright>
     <Authors>SmallChi</Authors>
     <PackageId>JT808</PackageId>