diff --git a/CMakeLists.txt b/CMakeLists.txt
index dcf6d9d4db..4cc99930cb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -228,6 +228,12 @@ message(STATUS "XPRESS support: ${USE_XPRESS}")
 if(BUILD_DOTNET)
   option(UNIVERSAL_DOTNET_PACKAGE "Build a .Net multi OS Package" OFF)
   message(STATUS ".Net: Create multiple os package: ${UNIVERSAL_DOTNET_PACKAGE}")
+
+  option(USE_DOTNET_TFM_31 "Use .Net Core 3.1 LTS support" ON)
+  message(STATUS ".Net: Use .Net Core 3.1 LTS support: ${USE_DOTNET_TFM_31}")
+
+  option(USE_DOTNET_TFM_60 "Use .Net 6.0 LTS support" ON)
+  message(STATUS ".Net: Use .Net 6.0 LTS support: ${USE_DOTNET_TFM_60}")
 endif()
 
 if(BUILD_JAVA)
diff --git a/cmake/dotnet.cmake b/cmake/dotnet.cmake
index d393f7e693..94af59ba55 100644
--- a/cmake/dotnet.cmake
+++ b/cmake/dotnet.cmake
@@ -30,6 +30,8 @@ endif()
 # Needed by dotnet/CMakeLists.txt
 set(DOTNET_PACKAGE Google.OrTools)
 set(DOTNET_PACKAGES_DIR "${PROJECT_BINARY_DIR}/dotnet/packages")
+
+# see: https://docs.microsoft.com/en-us/dotnet/core/rid-catalog
 if(APPLE)
   set(RUNTIME_IDENTIFIER osx-x64)
 elseif(UNIX)
@@ -44,6 +46,17 @@ message(STATUS ".Net runtime project: ${DOTNET_NATIVE_PROJECT}")
 set(DOTNET_NATIVE_PROJECT_DIR ${PROJECT_BINARY_DIR}/dotnet/${DOTNET_NATIVE_PROJECT})
 message(STATUS ".Net runtime project build path: ${DOTNET_NATIVE_PROJECT_DIR}")
 
+# see: https://docs.microsoft.com/en-us/dotnet/standard/frameworks
+if(USE_DOTNET_TFM_31 AND USE_DOTNET_TFM_60)
+  set(DOTNET_TFM "<TargetFrameworks>netcoreapp3.1;net6.0</TargetFrameworks>")
+elseif(USE_DOTNET_TFM_60)
+  set(DOTNET_TFM "<TargetFramework>net6.0</TargetFramework>")
+elseif(USE_DOTNET_TFM_31)
+  set(DOTNET_TFM "<TargetFramework>netcoreapp3.1</TargetFramework>")
+else()
+  message(FATAL_ERROR "No .Net SDK selected !")
+endif()
+
 set(DOTNET_PROJECT ${DOTNET_PACKAGE})
 message(STATUS ".Net project: ${DOTNET_PROJECT}")
 set(DOTNET_PROJECT_DIR ${PROJECT_BINARY_DIR}/dotnet/${DOTNET_PROJECT})
@@ -368,10 +381,18 @@ function(add_dotnet_sample FILE_NAME)
     WORKING_DIRECTORY ${DOTNET_SAMPLE_DIR})
 
   if(BUILD_TESTING)
-    add_test(
-      NAME dotnet_${COMPONENT_NAME}_${SAMPLE_NAME}
-      COMMAND ${DOTNET_EXECUTABLE} run --no-build --framework net6.0 -c Release
-      WORKING_DIRECTORY ${DOTNET_SAMPLE_DIR})
+    if(USE_DOTNET_TFM_31)
+      add_test(
+        NAME dotnet_${COMPONENT_NAME}_${SAMPLE_NAME}
+        COMMAND ${DOTNET_EXECUTABLE} run --no-build --framework netcoreapp3.1 -c Release
+        WORKING_DIRECTORY ${DOTNET_SAMPLE_DIR})
+    endif()
+    if(USE_DOTNET_TFM_60)
+      add_test(
+        NAME dotnet_${COMPONENT_NAME}_${SAMPLE_NAME}
+        COMMAND ${DOTNET_EXECUTABLE} run --no-build --framework net6.0 -c Release
+        WORKING_DIRECTORY ${DOTNET_SAMPLE_DIR})
+    endif()
   endif()
   message(STATUS "Configuring sample ${FILE_NAME} done")
 endfunction()
@@ -431,10 +452,18 @@ function(add_dotnet_example FILE_NAME)
     WORKING_DIRECTORY ${DOTNET_EXAMPLE_DIR})
 
   if(BUILD_TESTING)
-    add_test(
-      NAME dotnet_${COMPONENT_NAME}_${EXAMPLE_NAME}
-      COMMAND ${DOTNET_EXECUTABLE} run --no-build --framework net6.0 -c Release
-      WORKING_DIRECTORY ${DOTNET_EXAMPLE_DIR})
+    if(USE_DOTNET_TFM_31)
+      add_test(
+        NAME dotnet_${COMPONENT_NAME}_${EXAMPLE_NAME}
+        COMMAND ${DOTNET_EXECUTABLE} run --no-build --framework netcoreapp3.1 -c Release
+        WORKING_DIRECTORY ${DOTNET_EXAMPLE_DIR})
+    endif()
+    if(USE_DOTNET_TFM_60)
+      add_test(
+        NAME dotnet_${COMPONENT_NAME}_${EXAMPLE_NAME}
+        COMMAND ${DOTNET_EXECUTABLE} run --no-build --framework net6.0 -c Release
+        WORKING_DIRECTORY ${DOTNET_EXAMPLE_DIR})
+    endif()
   endif()
   message(STATUS "Configuring example ${FILE_NAME} done")
 endfunction()
diff --git a/makefiles/Makefile.dotnet.mk b/makefiles/Makefile.dotnet.mk
index a37e607160..74ea0aa341 100644
--- a/makefiles/Makefile.dotnet.mk
+++ b/makefiles/Makefile.dotnet.mk
@@ -87,6 +87,8 @@ $$(TEMP_DOTNET_DIR)/$1/%/%.csproj: \
 	$$(SED) -e "s/@DOTNET_PACKAGES_DIR@/..\/..\/..\/$(BUILD_DIR)\/dotnet\/packages/" \
  ortools$$Sdotnet$$SSample.csproj.in \
  > $$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
+	$$(SED) -i -e 's/@DOTNET_TFM@/<TargetFrameworks>netcoreapp3.1;net6.0<\/TargetFrameworks>/' \
+ $$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
 	$$(SED) -i -e 's/@DOTNET_PROJECT@/$$(DOTNET_ORTOOLS_ASSEMBLY_NAME)/' \
  $$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
 	$$(SED) -i -e 's/@SAMPLE_NAME@/$$*/' \
@@ -136,6 +138,8 @@ $$(TEMP_DOTNET_DIR)/$1/%/%.csproj: \
 	$$(SED) -e "s/@DOTNET_PACKAGES_DIR@/..\/..\/..\/$(BUILD_DIR)\/dotnet\/packages/" \
  ortools$$Sdotnet$$SSample.csproj.in \
  > $$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
+	$$(SED) -i -e 's/@DOTNET_TFM@/<TargetFrameworks>netcoreapp3.1;net6.0<\/TargetFrameworks>/' \
+ $$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
 	$$(SED) -i -e 's/@DOTNET_PROJECT@/$$(DOTNET_ORTOOLS_ASSEMBLY_NAME)/' \
  $$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
 	$$(SED) -i -e 's/@SAMPLE_NAME@/$$*/' \
@@ -184,6 +188,8 @@ $(TEMP_DOTNET_DIR)/tests/%/%.csproj: \
 	$(SED) -e "s/@DOTNET_PACKAGES_DIR@/..\/..\/..\/$(BUILD_DIR)\/dotnet\/packages/" \
  ortools$Sdotnet$STest.csproj.in \
  > $(TEMP_DOTNET_DIR)$Stests$S$*$S$*.csproj
+	$(SED) -i -e 's/@DOTNET_TFM@/<TargetFrameworks>netcoreapp3.1;net6.0<\/TargetFrameworks>/' \
+ $(TEMP_DOTNET_DIR)$Stests$S$*$S$*.csproj
 	$(SED) -i -e 's/@DOTNET_PROJECT@/$(DOTNET_ORTOOLS_ASSEMBLY_NAME)/' \
  $(TEMP_DOTNET_DIR)$Stests$S$*$S$*.csproj
 	$(SED) -i -e 's/@TEST_NAME@/$*/' \
@@ -483,6 +489,8 @@ $$(TEMP_DOTNET_DIR)/ortools_examples/examples/dotnet/%.csproj: \
 	$$(SED) -i -e 's/@PROJECT_VERSION_PATCH@/$$(GIT_REVISION)/' \
  $$(TEMP_DOTNET_DIR)$$Sortools_examples$$Sexamples$$Sdotnet$$S$$*.csproj
 	$(SED) -i -e 's/@DOTNET_PACKAGES_DIR@/./' \
+ $$(TEMP_DOTNET_DIR)$$Sortools_examples$$Sexamples$$Sdotnet$$S$$*.csproj
+	$(SED) -i -e 's/@DOTNET_TFM@/<TargetFrameworks>netcoreapp3.1;net6.0<\/TargetFrameworks>/' \
  $$(TEMP_DOTNET_DIR)$$Sortools_examples$$Sexamples$$Sdotnet$$S$$*.csproj
 	$(SED) -i -e 's/@DOTNET_PROJECT@/$$(DOTNET_ORTOOLS_ASSEMBLY_NAME)/' \
  $$(TEMP_DOTNET_DIR)$$Sortools_examples$$Sexamples$$Sdotnet$$S$$*.csproj
@@ -512,6 +520,8 @@ $$(TEMP_DOTNET_DIR)/ortools_examples/examples/dotnet/%.csproj: \
 	$$(SED) -i -e 's/@PROJECT_VERSION_PATCH@/$$(GIT_REVISION)/' \
  $$(TEMP_DOTNET_DIR)$$Sortools_examples$$Sexamples$$Sdotnet$$S$$*.csproj
 	$(SED) -i -e 's/@DOTNET_PACKAGES_DIR@/./' \
+ $$(TEMP_DOTNET_DIR)$$Sortools_examples$$Sexamples$$Sdotnet$$S$$*.csproj
+	$(SED) -i -e 's/@DOTNET_TFM@/<TargetFrameworks>netcoreapp3.1;net6.0<\/TargetFrameworks>/' \
  $$(TEMP_DOTNET_DIR)$$Sortools_examples$$Sexamples$$Sdotnet$$S$$*.csproj
 	$(SED) -i -e 's/@DOTNET_PROJECT@/$$(DOTNET_ORTOOLS_ASSEMBLY_NAME)/' \
  $$(TEMP_DOTNET_DIR)$$Sortools_examples$$Sexamples$$Sdotnet$$S$$*.csproj
@@ -570,7 +580,7 @@ nuget_archive: dotnet | $(TEMP_DOTNET_DIR)
 
 .PHONY: nuget_upload # Upload Nuget Package
 nuget_upload: nuget_archive
-	@echo Uploading Nuget package for "net6.0".
+	@echo Uploading Nuget package for "netcoreapp3.1;net6.0".
 	$(warning Not Implemented)
 
 endif  # HAS_DOTNET=ON
diff --git a/ortools/dotnet/Google.OrTools-full.csproj.in b/ortools/dotnet/Google.OrTools-full.csproj.in
index 6086f6071f..509a04f59a 100644
--- a/ortools/dotnet/Google.OrTools-full.csproj.in
+++ b/ortools/dotnet/Google.OrTools-full.csproj.in
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <LangVersion>9.0</LangVersion>
-    <TargetFrameworks>netcoreapp3.1;net6.0</TargetFrameworks>
+    @DOTNET_TFM@
     <RuntimeIdentifiers>win-x64;osx-x64;linux-x64</RuntimeIdentifiers>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <AssemblyName>@DOTNET_PROJECT@</AssemblyName>
diff --git a/ortools/dotnet/Google.OrTools-local.csproj.in b/ortools/dotnet/Google.OrTools-local.csproj.in
index 91359f336b..e9ec1bfeae 100644
--- a/ortools/dotnet/Google.OrTools-local.csproj.in
+++ b/ortools/dotnet/Google.OrTools-local.csproj.in
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <LangVersion>9.0</LangVersion>
-    <TargetFrameworks>netcoreapp3.1;net6.0</TargetFrameworks>
+    @DOTNET_TFM@
     <RuntimeIdentifier>@RUNTIME_IDENTIFIER@</RuntimeIdentifier>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <AssemblyName>@DOTNET_PROJECT@</AssemblyName>
diff --git a/ortools/dotnet/Google.OrTools.runtime.csproj.in b/ortools/dotnet/Google.OrTools.runtime.csproj.in
index d8f5893481..5cd5be36c0 100644
--- a/ortools/dotnet/Google.OrTools.runtime.csproj.in
+++ b/ortools/dotnet/Google.OrTools.runtime.csproj.in
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>netcoreapp3.1;net6.0</TargetFrameworks>
+    @DOTNET_TFM@
     <RuntimeIdentifier>@RUNTIME_IDENTIFIER@</RuntimeIdentifier>
     <AssemblyName>google-ortools-native</AssemblyName>
     <Version>@PROJECT_VERSION@</Version>
diff --git a/ortools/dotnet/Sample.csproj.in b/ortools/dotnet/Sample.csproj.in
index ff67990948..d13eae05bc 100644
--- a/ortools/dotnet/Sample.csproj.in
+++ b/ortools/dotnet/Sample.csproj.in
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <LangVersion>8.0</LangVersion>
-    <TargetFrameworks>net6.0</TargetFrameworks>
+    @DOTNET_TFM@
     <EnableDefaultItems>false</EnableDefaultItems>
     <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
     <!-- see https://github.com/dotnet/docs/issues/12237 -->
diff --git a/ortools/dotnet/Test.csproj.in b/ortools/dotnet/Test.csproj.in
index 8f67632944..1b7459b59b 100644
--- a/ortools/dotnet/Test.csproj.in
+++ b/ortools/dotnet/Test.csproj.in
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <LangVersion>8.0</LangVersion>
-    <TargetFrameworks>netcoreapp3.1;net6.0</TargetFrameworks>
+    @DOTNET_TFM@
     <EnableDefaultItems>false</EnableDefaultItems>
     <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
     <!-- see https://github.com/dotnet/docs/issues/12237 -->