WIP

VAR.WebFormsCore/Code/ExtensionMethods.cs

@@ -41,19 +41,39 @@ namespace VAR.WebFormsCore.Code
             context.Response.Body.WriteAsync(byteObject);
         }
 
+        public static void SafeSet(this IHeaderDictionary header, string key, string value)
+        {
+            if (header.ContainsKey(key))
+            {
+                header[key] = value;
+            }
+            else
+            {
+                header.Add(key, value);
+            }
+        }
+
+        public static void SafeDel(this IHeaderDictionary header, string key)
+        {
+            if (header.ContainsKey(key))
+            {
+                header.Remove(key);
+            }
+        }
+
         public static void PrepareCacheableResponse(this HttpResponse response)
         {
             const int secondsInDay = 86400;
-            response.Headers.Add("Cache-Control", string.Format("public, max-age={0}", secondsInDay));
+            response.Headers.SafeSet("Cache-Control", string.Format("public, max-age={0}", secondsInDay));
             string ExpireDate = DateTime.UtcNow.AddSeconds(secondsInDay).ToString("ddd, dd MMM yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture);
-            response.Headers.Add("Expires", ExpireDate + " GMT");
+            response.Headers.SafeSet("Expires", ExpireDate + " GMT");
         }
 
         public static void PrepareUncacheableResponse(this HttpResponse response)
         {
-            response.Headers.Add("Cache-Control", "max-age=0, no-cache, no-store");
+            response.Headers.SafeSet("Cache-Control", "max-age=0, no-cache, no-store");
             string ExpireDate = DateTime.UtcNow.AddSeconds(-1500).ToString("ddd, dd MMM yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture);
-            response.Headers.Add("Expires", ExpireDate + " GMT");
+            response.Headers.SafeSet("Expires", ExpireDate + " GMT");
         }
 
         #endregion HttpContext

VAR.WebFormsCore/Code/GlobalRouterMiddleware.cs

@@ -24,11 +24,11 @@ namespace VAR.WebFormsCore.Code
 
         public async Task Invoke(HttpContext httpContext)
         {
-            httpContext.Response.Headers.Remove("Server");
+            httpContext.Response.Headers.SafeDel("Server");
-            httpContext.Response.Headers.Remove("X-Powered-By");
+            httpContext.Response.Headers.SafeDel("X-Powered-By");
-            httpContext.Response.Headers.Add("X-Content-Type-Options", "nosniff");
+            httpContext.Response.Headers.SafeSet("X-Content-Type-Options", "nosniff");
-            httpContext.Response.Headers.Add("X-Frame-Options", "SAMEORIGIN");
+            httpContext.Response.Headers.SafeSet("X-Frame-Options", "SAMEORIGIN");
-            httpContext.Response.Headers.Add("X-XSS-Protection", "1; mode=block");
+            httpContext.Response.Headers.SafeSet("X-XSS-Protection", "1; mode=block");
 
             try
             {

VAR.WebFormsCore/Pages/Page.cs

@@ -59,7 +59,7 @@ namespace VAR.WebFormsCore.Pages
                 Render(stringWriter);
                 if (context.Response.HasStarted) { return; }
 
-                context.Response.Headers.Add("Content-Type", "text/html");
+                context.Response.Headers.SafeSet("Content-Type", "text/html");
                 byte[] byteObject = _utf8Econding.GetBytes(stringWriter.ToString());
                 await context.Response.Body.WriteAsync(byteObject);
             }

VAR.WebFormsCore/VAR.WebFormsCore.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <OutputType>Library</OutputType>
   </PropertyGroup>