How to send POST for both master and detail tables?

Question

Currently I am using the following post method and it is return error 500 internal server error. System.NullReferenceException: Object reference not set to an instance of an object. at WebApi.Controllers.OrderController.PostOrder(Order order)

        public async Task<ActionResult<Order>> PostOrder(Order order)
        {
            
            // order table
            _context.OrderRequests.Add(order);
            
            // orderitem table
            foreach (var item in order.OrderItems)
            {
                _context.OrderItems.Add(item);
            }
            
            await _context.SaveChangesAsync();

            return CreatedAtAction("GetOrder", new { id = order.OrderID}, order);
            
         }

What is wrong? How do I submit POST on both tables? Or do I have to create a separate web api controller for OrderItems?

System.NullReferenceException: Object reference not set to an instance of an object. at WebApi.Controllers.OrderController.PostOrder(Order order) in C:\dev\Test\WebApi\Controllers\OrderController.cs:line 91 at lambda_method(Closure , Object ) at Microsoft.Extensions.Internal.ObjectMethodExecutorAwaitable.Awaiter.GetResult() at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.AwaitableObjectResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask`1 actionResultValueTask) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope) at Microsoft.AspNetCore.Routing.EndpointMiddleware.g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger) at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context) at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

You need not create a separate API controller for nested items. I tried to replicate the scenario with a nested structure like yours (Parent class having a List<Child> classes as one of its members) and could post the data successfully. Model binding does not seem to have any issue. 500 could be because of a server side issue. Looking at the stacktrace of the exception could provide more information. — Sai Gummaluri
I added the whole exception details. I am using angular for front end. Do you think the problem would be there? Or at the asp.net core web api? — pepega

Roman Ryzhiy Roman Ryzhiy · Accepted Answer · 2020-08-27T06:59:53

Just save your changes to the context before adding "child" records:

    public async Task<ActionResult<Order>> PostOrder(Order order)
    {
        
        // order table
        _context.OrderRequests.Add(order);
        await _context.SaveChangesAsync();
        
        // orderitem table
        foreach (var item in order.OrderItems)
        {
            _context.OrderItems.Add(item);
        }
        
        await _context.SaveChangesAsync();

        return CreatedAtAction("GetOrder", new { id = order.OrderID}, order);
        
     }

How to send POST for both master and detail tables?

1 Answers