diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
index a9c7381ec4b..44ea744ea7b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
@@ -118,7 +118,7 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
         );
 
         mapTypes = new HashSet<>(
-                Arrays.asList("IDictionary")
+                Arrays.asList("IDictionary", "Dictionary")
         );
 
         // NOTE: C# uses camel cased reserved words, while models are title cased. We don't want lowercase comparisons.
@@ -712,7 +712,7 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
                             }
                         } else {
                             operation.returnContainer = operation.returnType;
-                            operation.isMap = this.mapTypes.contains(typeMapping);
+                            operation.isMap = this.mapTypes.stream().anyMatch(t -> typeMapping.startsWith(t));
                         }
                     }
 
diff --git a/modules/openapi-generator/src/main/resources/aspnetcore/2.0/mapReturn.mustache b/modules/openapi-generator/src/main/resources/aspnetcore/2.0/mapReturn.mustache
index 94f16e11fdc..0b63864f64e 100644
--- a/modules/openapi-generator/src/main/resources/aspnetcore/2.0/mapReturn.mustache
+++ b/modules/openapi-generator/src/main/resources/aspnetcore/2.0/mapReturn.mustache
@@ -1,4 +1,4 @@
 
             var example = exampleJson != null
-            ? JsonConvert.DeserializeObject<Dictionary<{{{returnType}}}>>(exampleJson)
-            : new Dictionary<{{{returnType}}}>();
\ No newline at end of file
+            ? JsonConvert.DeserializeObject<{{{returnType}}}>(exampleJson)
+            : new {{{returnType}}}();
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/resources/aspnetcore/2.1/mapReturn.mustache b/modules/openapi-generator/src/main/resources/aspnetcore/2.1/mapReturn.mustache
index 94f16e11fdc..0b63864f64e 100644
--- a/modules/openapi-generator/src/main/resources/aspnetcore/2.1/mapReturn.mustache
+++ b/modules/openapi-generator/src/main/resources/aspnetcore/2.1/mapReturn.mustache
@@ -1,4 +1,4 @@
 
             var example = exampleJson != null
-            ? JsonConvert.DeserializeObject<Dictionary<{{{returnType}}}>>(exampleJson)
-            : new Dictionary<{{{returnType}}}>();
\ No newline at end of file
+            ? JsonConvert.DeserializeObject<{{{returnType}}}>(exampleJson)
+            : new {{{returnType}}}();
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/resources/aspnetcore/3.0/mapReturn.mustache b/modules/openapi-generator/src/main/resources/aspnetcore/3.0/mapReturn.mustache
index 94f16e11fdc..0b63864f64e 100644
--- a/modules/openapi-generator/src/main/resources/aspnetcore/3.0/mapReturn.mustache
+++ b/modules/openapi-generator/src/main/resources/aspnetcore/3.0/mapReturn.mustache
@@ -1,4 +1,4 @@
 
             var example = exampleJson != null
-            ? JsonConvert.DeserializeObject<Dictionary<{{{returnType}}}>>(exampleJson)
-            : new Dictionary<{{{returnType}}}>();
\ No newline at end of file
+            ? JsonConvert.DeserializeObject<{{{returnType}}}>(exampleJson)
+            : new {{{returnType}}}();
\ No newline at end of file
diff --git a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Controllers/StoreApi.cs b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
index 2077313f7dd..31f24ebfc78 100644
--- a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
+++ b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
@@ -70,7 +70,7 @@ namespace Org.OpenAPITools.Controllers
             
             var example = exampleJson != null
             ? JsonConvert.DeserializeObject<Dictionary<string, int>>(exampleJson)
-            : default(Dictionary<string, int>);
+            : new Dictionary<string, int>();
             //TODO: Change the data returned
             return new ObjectResult(example);
         }
diff --git a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Controllers/StoreApi.cs b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Controllers/StoreApi.cs
index 2077313f7dd..31f24ebfc78 100644
--- a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Controllers/StoreApi.cs
+++ b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Controllers/StoreApi.cs
@@ -70,7 +70,7 @@ namespace Org.OpenAPITools.Controllers
             
             var example = exampleJson != null
             ? JsonConvert.DeserializeObject<Dictionary<string, int>>(exampleJson)
-            : default(Dictionary<string, int>);
+            : new Dictionary<string, int>();
             //TODO: Change the data returned
             return new ObjectResult(example);
         }
diff --git a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Controllers/StoreApi.cs b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
index 2077313f7dd..31f24ebfc78 100644
--- a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
+++ b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
@@ -70,7 +70,7 @@ namespace Org.OpenAPITools.Controllers
             
             var example = exampleJson != null
             ? JsonConvert.DeserializeObject<Dictionary<string, int>>(exampleJson)
-            : default(Dictionary<string, int>);
+            : new Dictionary<string, int>();
             //TODO: Change the data returned
             return new ObjectResult(example);
         }
diff --git a/samples/server/petstore/aspnetcore-6.0-pocoModels/src/Org.OpenAPITools/Controllers/StoreApi.cs b/samples/server/petstore/aspnetcore-6.0-pocoModels/src/Org.OpenAPITools/Controllers/StoreApi.cs
index 2077313f7dd..31f24ebfc78 100644
--- a/samples/server/petstore/aspnetcore-6.0-pocoModels/src/Org.OpenAPITools/Controllers/StoreApi.cs
+++ b/samples/server/petstore/aspnetcore-6.0-pocoModels/src/Org.OpenAPITools/Controllers/StoreApi.cs
@@ -70,7 +70,7 @@ namespace Org.OpenAPITools.Controllers
             
             var example = exampleJson != null
             ? JsonConvert.DeserializeObject<Dictionary<string, int>>(exampleJson)
-            : default(Dictionary<string, int>);
+            : new Dictionary<string, int>();
             //TODO: Change the data returned
             return new ObjectResult(example);
         }
diff --git a/samples/server/petstore/aspnetcore-6.0-project4Models/src/Org.OpenAPITools/Controllers/StoreApi.cs b/samples/server/petstore/aspnetcore-6.0-project4Models/src/Org.OpenAPITools/Controllers/StoreApi.cs
index 2077313f7dd..31f24ebfc78 100644
--- a/samples/server/petstore/aspnetcore-6.0-project4Models/src/Org.OpenAPITools/Controllers/StoreApi.cs
+++ b/samples/server/petstore/aspnetcore-6.0-project4Models/src/Org.OpenAPITools/Controllers/StoreApi.cs
@@ -70,7 +70,7 @@ namespace Org.OpenAPITools.Controllers
             
             var example = exampleJson != null
             ? JsonConvert.DeserializeObject<Dictionary<string, int>>(exampleJson)
-            : default(Dictionary<string, int>);
+            : new Dictionary<string, int>();
             //TODO: Change the data returned
             return new ObjectResult(example);
         }
diff --git a/samples/server/petstore/aspnetcore-6.0/src/Org.OpenAPITools/Controllers/StoreApi.cs b/samples/server/petstore/aspnetcore-6.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
index 2077313f7dd..31f24ebfc78 100644
--- a/samples/server/petstore/aspnetcore-6.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
+++ b/samples/server/petstore/aspnetcore-6.0/src/Org.OpenAPITools/Controllers/StoreApi.cs
@@ -70,7 +70,7 @@ namespace Org.OpenAPITools.Controllers
             
             var example = exampleJson != null
             ? JsonConvert.DeserializeObject<Dictionary<string, int>>(exampleJson)
-            : default(Dictionary<string, int>);
+            : new Dictionary<string, int>();
             //TODO: Change the data returned
             return new ObjectResult(example);
         }
diff --git a/samples/server/petstore/aspnetcore/src/Org.OpenAPITools/Controllers/StoreApi.cs b/samples/server/petstore/aspnetcore/src/Org.OpenAPITools/Controllers/StoreApi.cs
index 9ce84426e29..f815bf39011 100644
--- a/samples/server/petstore/aspnetcore/src/Org.OpenAPITools/Controllers/StoreApi.cs
+++ b/samples/server/petstore/aspnetcore/src/Org.OpenAPITools/Controllers/StoreApi.cs
@@ -70,7 +70,7 @@ namespace Org.OpenAPITools.Controllers
             
             var example = exampleJson != null
             ? JsonConvert.DeserializeObject<Dictionary<string, int>>(exampleJson)
-            : default(Dictionary<string, int>);
+            : new Dictionary<string, int>();
             //TODO: Change the data returned
             return new ObjectResult(example);
         }