fix npe :Unboxing of '(count < numVars) ? true : null' produce npe (#5917)

* fix npe :Unboxing of '(count < numVars) ? true : null' may produce 'java.lang.NullPointerException

* add test to cover reconcileInlineEnums method.

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/CSharpClientCodegen.java

@@ -555,7 +555,7 @@ public class CSharpClientCodegen extends AbstractCSharpCodegen {
                 int count = 0, numVars = codegenProperties.size();
                 for(CodegenProperty codegenProperty : codegenProperties) {
                     count += 1;
-                    codegenProperty.hasMore = (count < numVars) ? true : null;
+                    codegenProperty.hasMore = count < numVars;
                 }
                 codegenModel.vars = codegenProperties;
             }

modules/swagger-codegen/src/test/java/io/swagger/codegen/csharp/CsharpModelEnumTest.java

@@ -0,0 +1,75 @@
+package io.swagger.codegen.csharp;
+
+
+import io.swagger.codegen.CodegenModel;
+import io.swagger.codegen.CodegenProperty;
+import io.swagger.codegen.DefaultCodegen;
+import io.swagger.codegen.languages.CSharpClientCodegen;
+import io.swagger.models.ComposedModel;
+import io.swagger.models.Model;
+import io.swagger.models.ModelImpl;
+import io.swagger.models.RefModel;
+import io.swagger.models.properties.Property;
+import io.swagger.models.properties.StringProperty;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+public class CsharpModelEnumTest {
+    @Test(description = "not override identical parent enums")
+    public void overrideEnumTest() {
+        final StringProperty identicalEnumProperty = new StringProperty();
+        identicalEnumProperty.setEnum(Arrays.asList("VALUE1", "VALUE2", "VALUE3"));
+
+        final StringProperty subEnumProperty = new StringProperty();
+        subEnumProperty.setEnum(Arrays.asList("SUB1", "SUB2", "SUB3"));
+
+        // Add one enum property to the parent
+        final Map<String, Property> parentProperties = new HashMap<String, Property>();
+        parentProperties.put("sharedThing", identicalEnumProperty);
+
+        // Add TWO enums to the subType model; one of which is identical to the one in parent class
+        final Map<String, Property> subProperties = new HashMap<String, Property>();
+        subProperties.put("sharedThing", identicalEnumProperty);
+        subProperties.put("unsharedThing", identicalEnumProperty);
+
+        final ModelImpl parentModel = new ModelImpl()
+                .description("parentModel");
+        parentModel.setProperties(parentProperties);
+        parentModel.name("parentModel");
+
+        final ModelImpl subModel = new ModelImpl()
+                .description("subModel");
+        subModel.setProperties(subProperties);
+        subModel.name("subModel");
+
+        final ComposedModel model = new ComposedModel()
+                .parent(new RefModel(parentModel.getName()))
+                .child(subModel)
+                .interfaces(new ArrayList<RefModel>());
+
+        final DefaultCodegen codegen = new CSharpClientCodegen();
+        final Map<String, Model> allModels = new HashMap<>();
+        allModels.put("ParentModel", parentModel);
+        allModels.put("SubModel", subModel);
+
+        final CodegenModel cm = codegen.fromModel("sample", model, allModels);
+
+        Assert.assertEquals(cm.name, "sample");
+        Assert.assertEquals(cm.classname, "Sample");
+        Assert.assertEquals(cm.parent, "ParentModel");
+        Assert.assertTrue(cm.imports.contains("ParentModel"));
+
+        // Assert that only the unshared/uninherited enum remains
+        Assert.assertEquals(cm.vars.size(), 1);
+        final CodegenProperty enumVar = cm.vars.get(0);
+        Assert.assertEquals(enumVar.baseName, "unsharedThing");
+        Assert.assertEquals(enumVar.datatype, "string");
+        Assert.assertEquals(enumVar.datatypeWithEnum, "UnsharedThingEnum");
+        Assert.assertTrue(enumVar.isEnum);
+    }
+}