Fix issue: 16313 - Administrator can create two same roles

src/Orchard.Web/Modules/Orchard.Roles/Controllers/AdminController.cs

@@ -77,6 +77,15 @@ namespace Orchard.Roles.Controllers {
             var viewModel = new RoleCreateViewModel();
             try {
                 UpdateModel(viewModel);
+
+                //check if the role name already exists
+                if (!_roleService.VerifyRoleUnicity(viewModel.Name))
+                {
+                    Services.Notifier.Error(T("Creating Role failed: {0}", "Role with same name already exists"));
+                    
+                    return RedirectToAction("Create");
+                }
+
                 _roleService.CreateRole(viewModel.Name);
                 foreach (string key in Request.Form.Keys) {
                     if (key.StartsWith("Checkbox.") && Request.Form[key] == "true") {

src/Orchard.Web/Modules/Orchard.Roles/Services/IRoleService.cs

@@ -15,5 +15,13 @@ namespace Orchard.Roles.Services {
         IEnumerable<string> GetPermissionsForRole(int id);
 
         IEnumerable<string> GetPermissionsForRoleByName(string name);
+
+
+        /// <summary>
+        /// Verify if the role name is unique
+        /// </summary>
+        /// <param name="name">Role name</param>
+        /// <returns>Returns false if a role with the given name already exits</returns>
+        bool VerifyRoleUnicity(string name);
     }
 }

src/Orchard.Web/Modules/Orchard.Roles/Services/RoleService.cs

@@ -151,6 +151,17 @@ namespace Orchard.Roles.Services {
             });
         }
 
+        /// <summary>
+        /// Verify if the role name is unique
+        /// </summary>
+        /// <param name="name">Role name</param>
+        /// <returns>Returns false if a role with the given name already exits</returns>
+        public bool VerifyRoleUnicity(string name) 
+        {
+            return _roleRepository.Get(x => x.Name == name) == null ? true : false;
+        }
+        
+
         IEnumerable<string> GetPermissionsForRoleByNameInner(string name) {
             var roleRecord = GetRoleByName(name);
             return roleRecord == null ? Enumerable.Empty<string>() : GetPermissionsForRole(roleRecord.Id);