Add TypeConverter for enum

Author: yilinjuang

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AspNetCoreServerCodegen.java

@@ -327,6 +327,7 @@ public void processOpts() {
         supportingFiles.add(new SupportingFile("Solution.mustache", "", packageName + ".sln"));
         supportingFiles.add(new SupportingFile("gitignore", packageFolder, ".gitignore"));
         supportingFiles.add(new SupportingFile("validateModel.mustache", packageFolder + File.separator + "Attributes", "ValidateModelStateAttribute.cs"));
+        supportingFiles.add(new SupportingFile("typeConverter.mustache", packageFolder + File.separator + "Converters", "CustomEnumConverter.cs"));
         supportingFiles.add(new SupportingFile("Project.csproj.mustache", packageFolder, packageName + ".csproj"));
         if (!isLibrary) {
             supportingFiles.add(new SupportingFile("Dockerfile.mustache", packageFolder, "Dockerfile"));

modules/openapi-generator/src/main/resources/aspnetcore/2.1/enumClass.mustache

@@ -5,7 +5,8 @@
         {{#description}}
         /// <value>{{{description}}}</value>
         {{/description}}
-        {{#allowableValues}}{{#enumVars}}{{#-first}}{{#isString}}[JsonConverter(typeof(Newtonsoft.Json.Converters.StringEnumConverter))]{{/isString}}{{/-first}}{{/enumVars}}{{/allowableValues}}
+        {{#allowableValues}}{{#enumVars}}{{#-first}}{{#isString}}[TypeConverter(typeof(CustomEnumConverter<{{#datatypeWithEnum}}{{.}}{{/datatypeWithEnum}}{{^datatypeWithEnum}}{{classname}}{{/datatypeWithEnum}}>))]
+        [JsonConverter(typeof(Newtonsoft.Json.Converters.StringEnumConverter))]{{/isString}}{{/-first}}{{/enumVars}}{{/allowableValues}}
         public enum {{#datatypeWithEnum}}{{.}}{{/datatypeWithEnum}}{{^datatypeWithEnum}}{{classname}}{{/datatypeWithEnum}}
         {
             {{#allowableValues}}{{#enumVars}}

modules/openapi-generator/src/main/resources/aspnetcore/2.1/model.mustache

@@ -3,9 +3,11 @@ using System;
 using System.Linq;
 using System.Text;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
 using System.Runtime.Serialization;
 using Newtonsoft.Json;
+using {{packageName}}.Converters;
 
 {{#models}}
 {{#model}}

modules/openapi-generator/src/main/resources/aspnetcore/2.1/typeConverter.mustache

@@ -0,0 +1,33 @@
+using System;
+using System.ComponentModel;
+using System.Globalization;
+using Newtonsoft.Json;
+
+namespace {{packageName}}.Converters
+{
+    /// <summary>
+    /// Custom string to enum converter
+    /// </summary>
+    public class CustomEnumConverter<T> : TypeConverter
+    {
+        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+        {
+            if (sourceType == typeof(string))
+            {
+                return true;
+            }
+            return base.CanConvertFrom(context, sourceType);
+        }
+
+        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        {
+            var s = value as string;
+            if (string.IsNullOrEmpty(s))
+            {
+                return null;
+            }
+
+            return JsonConvert.DeserializeObject<T>(@"""" + value.ToString() + @"""");
+        }
+    }
+}