diff --git a/modules/openapi-generator/src/main/resources/aspnetcore/3.0/model.mustache b/modules/openapi-generator/src/main/resources/aspnetcore/3.0/model.mustache
index 917e3680492..312cbf6b483 100644
--- a/modules/openapi-generator/src/main/resources/aspnetcore/3.0/model.mustache
+++ b/modules/openapi-generator/src/main/resources/aspnetcore/3.0/model.mustache
@@ -55,7 +55,7 @@ namespace {{modelPackage}}
         [MinLength({{minLength}})]{{/maxLength}}{{/minLength}}{{^minLength}}{{#maxLength}}
         [MaxLength({{.}})]{{/maxLength}}{{/minLength}}{{#minimum}}{{#maximum}}
         [Range({{minimum}}, {{maximum}})]{{/maximum}}{{/minimum}}
-        [DataMember(Name="{{baseName}}", EmitDefaultValue={{#isNullable}}true{{/isNullable}}{{^isNullable}}false{{/isNullable}})]
+        [DataMember(Name="{{baseName}}", EmitDefaultValue={{#isNullable}}true{{/isNullable}}{{^isNullable}}{{#vendorExtensions.x-is-value-type}}true{{/vendorExtensions.x-is-value-type}}{{^vendorExtensions.x-is-value-type}}false{{/vendorExtensions.x-is-value-type}}{{/isNullable}})]
         {{#isEnum}}
         public {{{datatypeWithEnum}}}{{#isNullable}}?{{/isNullable}} {{name}} { get; set; }{{#defaultValue}} = {{{.}}};{{/defaultValue}}
         {{/isEnum}}
diff --git a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/ApiResponse.cs b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/ApiResponse.cs
index 88e45fce388..7573feaf410 100644
--- a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/ApiResponse.cs
+++ b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/ApiResponse.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Code
         /// </summary>
-        [DataMember(Name="code", EmitDefaultValue=false)]
+        [DataMember(Name="code", EmitDefaultValue=true)]
         public int Code { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Category.cs b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Category.cs
index e147a10073c..810f5beacc2 100644
--- a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Category.cs
+++ b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Category.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Order.cs b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Order.cs
index e9013f0ed0d..1d972579269 100644
--- a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Order.cs
+++ b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Order.cs
@@ -29,19 +29,19 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
         /// Gets or Sets PetId
         /// </summary>
-        [DataMember(Name="petId", EmitDefaultValue=false)]
+        [DataMember(Name="petId", EmitDefaultValue=true)]
         public long PetId { get; set; }
 
         /// <summary>
         /// Gets or Sets Quantity
         /// </summary>
-        [DataMember(Name="quantity", EmitDefaultValue=false)]
+        [DataMember(Name="quantity", EmitDefaultValue=true)]
         public int Quantity { get; set; }
 
         /// <summary>
@@ -83,13 +83,13 @@ namespace Org.OpenAPITools.Models
         /// Order Status
         /// </summary>
         /// <value>Order Status</value>
-        [DataMember(Name="status", EmitDefaultValue=false)]
+        [DataMember(Name="status", EmitDefaultValue=true)]
         public StatusEnum Status { get; set; }
 
         /// <summary>
         /// Gets or Sets Complete
         /// </summary>
-        [DataMember(Name="complete", EmitDefaultValue=false)]
+        [DataMember(Name="complete", EmitDefaultValue=true)]
         public bool Complete { get; set; } = false;
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Pet.cs b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Pet.cs
index d5a816cd5ee..762279e4d6d 100644
--- a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Pet.cs
+++ b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Pet.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
@@ -91,7 +91,7 @@ namespace Org.OpenAPITools.Models
         /// pet status in the store
         /// </summary>
         /// <value>pet status in the store</value>
-        [DataMember(Name="status", EmitDefaultValue=false)]
+        [DataMember(Name="status", EmitDefaultValue=true)]
         public StatusEnum Status { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Tag.cs b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Tag.cs
index 090f95cc494..5153ae0c4bb 100644
--- a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Tag.cs
+++ b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/Tag.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/User.cs b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/User.cs
index 4c6d96d08c5..a64c031e615 100644
--- a/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/User.cs
+++ b/samples/server/petstore/aspnetcore-3.0/src/Org.OpenAPITools/Models/User.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
@@ -72,7 +72,7 @@ namespace Org.OpenAPITools.Models
         /// User Status
         /// </summary>
         /// <value>User Status</value>
-        [DataMember(Name="userStatus", EmitDefaultValue=false)]
+        [DataMember(Name="userStatus", EmitDefaultValue=true)]
         public int UserStatus { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/ApiResponse.cs b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/ApiResponse.cs
index 88e45fce388..7573feaf410 100644
--- a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/ApiResponse.cs
+++ b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/ApiResponse.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Code
         /// </summary>
-        [DataMember(Name="code", EmitDefaultValue=false)]
+        [DataMember(Name="code", EmitDefaultValue=true)]
         public int Code { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Category.cs b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Category.cs
index e147a10073c..810f5beacc2 100644
--- a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Category.cs
+++ b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Category.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Order.cs b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Order.cs
index e9013f0ed0d..1d972579269 100644
--- a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Order.cs
+++ b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Order.cs
@@ -29,19 +29,19 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
         /// Gets or Sets PetId
         /// </summary>
-        [DataMember(Name="petId", EmitDefaultValue=false)]
+        [DataMember(Name="petId", EmitDefaultValue=true)]
         public long PetId { get; set; }
 
         /// <summary>
         /// Gets or Sets Quantity
         /// </summary>
-        [DataMember(Name="quantity", EmitDefaultValue=false)]
+        [DataMember(Name="quantity", EmitDefaultValue=true)]
         public int Quantity { get; set; }
 
         /// <summary>
@@ -83,13 +83,13 @@ namespace Org.OpenAPITools.Models
         /// Order Status
         /// </summary>
         /// <value>Order Status</value>
-        [DataMember(Name="status", EmitDefaultValue=false)]
+        [DataMember(Name="status", EmitDefaultValue=true)]
         public StatusEnum Status { get; set; }
 
         /// <summary>
         /// Gets or Sets Complete
         /// </summary>
-        [DataMember(Name="complete", EmitDefaultValue=false)]
+        [DataMember(Name="complete", EmitDefaultValue=true)]
         public bool Complete { get; set; } = false;
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Pet.cs b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Pet.cs
index d5a816cd5ee..762279e4d6d 100644
--- a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Pet.cs
+++ b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Pet.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
@@ -91,7 +91,7 @@ namespace Org.OpenAPITools.Models
         /// pet status in the store
         /// </summary>
         /// <value>pet status in the store</value>
-        [DataMember(Name="status", EmitDefaultValue=false)]
+        [DataMember(Name="status", EmitDefaultValue=true)]
         public StatusEnum Status { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Tag.cs b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Tag.cs
index 090f95cc494..5153ae0c4bb 100644
--- a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Tag.cs
+++ b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/Tag.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/User.cs b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/User.cs
index 4c6d96d08c5..a64c031e615 100644
--- a/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/User.cs
+++ b/samples/server/petstore/aspnetcore-3.1/src/Org.OpenAPITools/Models/User.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
@@ -72,7 +72,7 @@ namespace Org.OpenAPITools.Models
         /// User Status
         /// </summary>
         /// <value>User Status</value>
-        [DataMember(Name="userStatus", EmitDefaultValue=false)]
+        [DataMember(Name="userStatus", EmitDefaultValue=true)]
         public int UserStatus { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/ApiResponse.cs b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/ApiResponse.cs
index 88e45fce388..7573feaf410 100644
--- a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/ApiResponse.cs
+++ b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/ApiResponse.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Code
         /// </summary>
-        [DataMember(Name="code", EmitDefaultValue=false)]
+        [DataMember(Name="code", EmitDefaultValue=true)]
         public int Code { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Category.cs b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Category.cs
index 8b9fd03a240..0d63dc9d7e6 100644
--- a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Category.cs
+++ b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Category.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Order.cs b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Order.cs
index e9013f0ed0d..1d972579269 100644
--- a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Order.cs
+++ b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Order.cs
@@ -29,19 +29,19 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
         /// Gets or Sets PetId
         /// </summary>
-        [DataMember(Name="petId", EmitDefaultValue=false)]
+        [DataMember(Name="petId", EmitDefaultValue=true)]
         public long PetId { get; set; }
 
         /// <summary>
         /// Gets or Sets Quantity
         /// </summary>
-        [DataMember(Name="quantity", EmitDefaultValue=false)]
+        [DataMember(Name="quantity", EmitDefaultValue=true)]
         public int Quantity { get; set; }
 
         /// <summary>
@@ -83,13 +83,13 @@ namespace Org.OpenAPITools.Models
         /// Order Status
         /// </summary>
         /// <value>Order Status</value>
-        [DataMember(Name="status", EmitDefaultValue=false)]
+        [DataMember(Name="status", EmitDefaultValue=true)]
         public StatusEnum Status { get; set; }
 
         /// <summary>
         /// Gets or Sets Complete
         /// </summary>
-        [DataMember(Name="complete", EmitDefaultValue=false)]
+        [DataMember(Name="complete", EmitDefaultValue=true)]
         public bool Complete { get; set; } = false;
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Pet.cs b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Pet.cs
index d5a816cd5ee..762279e4d6d 100644
--- a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Pet.cs
+++ b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Pet.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
@@ -91,7 +91,7 @@ namespace Org.OpenAPITools.Models
         /// pet status in the store
         /// </summary>
         /// <value>pet status in the store</value>
-        [DataMember(Name="status", EmitDefaultValue=false)]
+        [DataMember(Name="status", EmitDefaultValue=true)]
         public StatusEnum Status { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Tag.cs b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Tag.cs
index 090f95cc494..5153ae0c4bb 100644
--- a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Tag.cs
+++ b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/Tag.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
diff --git a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/User.cs b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/User.cs
index 4c6d96d08c5..a64c031e615 100644
--- a/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/User.cs
+++ b/samples/server/petstore/aspnetcore-5.0/src/Org.OpenAPITools/Models/User.cs
@@ -29,7 +29,7 @@ namespace Org.OpenAPITools.Models
         /// <summary>
         /// Gets or Sets Id
         /// </summary>
-        [DataMember(Name="id", EmitDefaultValue=false)]
+        [DataMember(Name="id", EmitDefaultValue=true)]
         public long Id { get; set; }
 
         /// <summary>
@@ -72,7 +72,7 @@ namespace Org.OpenAPITools.Models
         /// User Status
         /// </summary>
         /// <value>User Status</value>
-        [DataMember(Name="userStatus", EmitDefaultValue=false)]
+        [DataMember(Name="userStatus", EmitDefaultValue=true)]
         public int UserStatus { get; set; }
 
         /// <summary>