Fix csharp-netcore enum var name underscore handling (#8213)

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

@@ -787,8 +787,7 @@ public String toEnumVarName(String value, String datatype) {
         }
 
         // string
-        String var = value.replaceAll("_", " ");
-        //var = WordUtils.capitalizeFully(var);
+        String var = value.replaceAll(" ", "_");
         var = camelize(var);
         var = var.replaceAll("\\W+", "");
 

modules/openapi-generator/src/test/java/org/openapitools/codegen/csharpnetcore/CSharpNetCoreClientCodegenTest.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2020 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.openapitools.codegen.csharp;
+
+import org.openapitools.codegen.languages.CSharpNetCoreClientCodegen;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+public class CSharpNetCoreClientCodegenTest {
+
+    @Test
+    public void testToEnumVarName() throws Exception {
+        final CSharpNetCoreClientCodegen codegen = new CSharpNetCoreClientCodegen();
+        codegen.processOpts();
+
+        Assert.assertEquals(codegen.toEnumVarName("FooBar", "string"), "FooBar");
+        Assert.assertEquals(codegen.toEnumVarName("fooBar", "string"), "FooBar");
+        Assert.assertEquals(codegen.toEnumVarName("foo-bar", "string"), "FooBar");
+        Assert.assertEquals(codegen.toEnumVarName("foo_bar", "string"), "FooBar");
+        Assert.assertEquals(codegen.toEnumVarName("foo bar", "string"), "FooBar");
+
+        // The below cases do not work currently, camelize doesn't support uppercase
+        // Assert.assertEquals(codegen.toEnumVarName("FOO-BAR", "string"), "FooBar");
+        // Assert.assertEquals(codegen.toEnumVarName("FOO_BAR", "string"), "FooBar");
+    }
+}