ASP.NET Core .NET 8 receives null form values from certain iPhone 13 Pro Max devices

Question

Question

Answer 1

Bruce (SqlWork.com) 85,786

if you have a real iPhone device, you can debug remotely with safari on a Mac.

plug the iPhone into your mac and trust.
on the iPhone under safari advanced setting enable web inspector.
on the Mac under safari setting enable developer tools
then open safari on the mac, open web inspector, and attach to the iPhone safari.

you can debug the javascript and use the network monitor to see what is actually sent.

note: I have never used, but there is similar support for chrome if you prefer the chrome debugger.

0 comments

Answer 2

These are my code samples

**Controller
** public async Task<IActionResult> Get([FromForm] BuyInsuranceDTO b)

{

    //if (!User.HasClaim("Permission", Permissions.PurchasePolicy))

    //{

    //    return StatusCode(403, new

    //    {

    //        success = false,

    //        message = "Sorry, you cant purchase policy at the moment."

    //    });

    //}



    var loggedInCustomer = Convert.ToInt16(User.FindFirst(ClaimTypes.NameIdentifier)?.Value);

    var upload = Request.Form.Files.Where(x => x.Name == "Identification").FirstOrDefault();

    var createPolicy = await service.CreateService(b, upload, loggedInCustomer, User.Identity.IsAuthenticated);

    if (!createPolicy.Success)

    {

        return Json(new MyResponse { Success = false, Message = createPolicy.Message });

    }

    return Json(new MyResponse { Success = true, Message = createPolicy.Message });

}**  
```DTO  
**    public class BuyInsuranceDTO

```powershell
{

    // ================= BASIC =================

    [Required]

    public string FirstName { get; set; }

    [Required]

    public string LastName { get; set; }

    public string MiddleName { get; set; }

    [Required]

    [Range(1, 2)]

    public int Sex { get; set; }

    [Required]

    public DateTime DOB { get; set; }

    [Required]

    public string PhoneNumber { get; set; }

    [Required]

    public string Address { get; set; }

    public string EmailAddress { get; set; }

    public string Agent { get; set; }

    // ================= NEXT OF KIN =================

    [Required]

    public string NOKFullName { get; set; }

    public int NOKRelationship { get; set; }

    [Required]

    public string NOKPhoneNumber { get; set; }

    [Required]

    public string NOKAddress { get; set; }

    // ================= POLICY =================

    public Guid? PolicyID { get; set; }

    [Required]

    public List<CoverItemDTO> Covers { get; set; }

    // ================= IDENTIFICATION =================

    [Required]

    public int IdentificationTypeId { get; set; }

    [Required]

    public string IdentificationNumber { get; set; }

    public DateTime? ExpiryDate { get; set; }

    public IFormFile Identification { get; set; }

    // ================= BUSSINESS ADDRESS =================

    public string StreetNumber { get; set; }

    [Required]

    public string StreetName { get; set; }

    public string LandMark { get; set; }

    [Required]

    public int StateID { get; set; }

    [Required]

    public int LGAID { get; set; }

    [Required]

    public int AccountID { get; set; }

    // ================= COVER UPLOADS =================

    public List<CoverFileUploadDTO> CoverFiles { get; set; }

    //============ Declared Items=================

    public List<DeclarationItemsDTO> DeclarationItems { get; set; }

}
```**Java Script  
**async function handleFinalSubmission() {

```javascript
if (!confirm('Are you sure you want to submit this policy application?')) {

    return;

}

const formData = buildPolicyFormData();

const result = await sendPolicy(formData);

if (!result) {

    return;

}

alert(result.message);

if (result.success) {

    window.location.href =

        '/policylisting/insuranceproduct';

}
```}

async function sendPolicy(formData) {

```typescript
if (isSubmitting) return;

isSubmitting = true;

showLoader();

try {

    const res = await fetch(`/policyListing/get`, {

        method: 'POST',

        body: formData

    });

    const data = await res.json();

    return data;

} catch (err) {

    console.error(err);

    alert("Failed to submit policy");

    return null;

} finally {

    isSubmitting = false;

    hideLoader();

}
```}

  
function appendIfExists(formData, key, elementId) {

```sql
const el = document.getElementById(elementId);

if (el)

    formData.append(key, el.value.trim());
```}

function buildPolicyFormData() {

```javascript
const formData = new FormData();

appendIfExists(formData, "FirstName", "firstName");

appendIfExists(formData, "MiddleName", "middleName");

appendIfExists(formData, "LastName", "lastName");

appendIfExists(formData, "PhoneNumber", "phone");

appendIfExists(formData, "Sex", "sex");

appendIfExists(formData, "DOB", "dob");

appendIfExists(formData, "Agent", "agent");

appendIfExists(formData, "Address", "address");

appendIfExists(formData, "EmailAddress", "email");

appendIfExists(formData, "NOKFullName", "nokName");

appendIfExists(formData, "NOKRelationship", "nokRelationship");

appendIfExists(formData, "NOKPhoneNumber", "nokPhone");

appendIfExists(formData, "NOKAddress", "nokAddress");

appendIfExists(formData, "IdentificationTypeId", "idType");

appendIfExists(formData, "IdentificationNumber", "idNumber");

appendIfExists(formData, "ExpiryDate", "expiryDate");

appendIfExists(formData, "StateID", "businessState");

appendIfExists(formData, "LGAID", "businessLga");

appendIfExists(formData, "StreetNumber", "businessStreetNumber");

appendIfExists(formData, "StreetName", "businessAddress");

appendIfExists(formData, "LandMark", "businessLandmark");

const idFile = document.getElementById('idUpload')?.files[0];

if (idFile) formData.append("Identification", idFile);

if (policyId) {

    formData.append("PolicyID", policyId);

}

// Covers

if (isCustomPolicy && selectedCovers.length > 0) {

    selectedCovers.forEach((cover, i) => {

        formData.append(`Covers[${i}].CoverID`, cover.CoverID);

        formData.append(`Covers[${i}].RiskCovered`, coverRisks[cover.CoverID] || 0);

    });

} else if (selectedCoverIds.length > 0) {

    selectedCoverIds.forEach((id, i) => {

        formData.append(`Covers[${i}].CoverID`, id);

    });

}

// Dynamic Cover Files

let fileIndex = 0;

let itemIndex = 0;

document.querySelectorAll('.cover-upload').forEach(input => {

    const file = input.files[0];

    if (file) {

        formData.append(`CoverFiles[${fileIndex}].File`, file);

        formData.append(`CoverFiles[${fileIndex}].CoverId`, input.dataset.coverid);

        formData.append(`CoverFiles[${fileIndex}].Label`, input.dataset.label);

        formData.append(`CoverFiles[${fileIndex}].coverUploadRequirementID`, input.name);

        fileIndex++;

    }

});

// Declaration Items

document.querySelectorAll("#tblDeclarationItems tbody tr").forEach(row => {

    const itemName = row.querySelector(".item-name")?.value.trim();

    const amount = row.querySelector(".item-amount")?.value;

    // Ignore empty rows

    if (!itemName || !amount)

        return;

    formData.append(`DeclarationItems[${itemIndex}].ItemName`, itemName);

    formData.append(`DeclarationItems[${itemIndex}].Amount`, amount);

    itemIndex++;

});

return formData;
```}

paul levey 0 Reputation points

2026-11-02T05:46:48.77+00:00

******@paullevey.net

Answer 3

Paul Thomas 160

One likely cause that fits "only some iPhones" is the request body size limit. By default, ASP.NET Core rejects request bodies larger than 30,000,000 bytes (about 28.6 MB), and IIS and IIS Express have the same default limit. Photos from newer iPhones can push a multipart request over that, especially ProRAW images or several photos in one form, so one iPhone 13 Pro Max can work while another, with different photos or camera settings, fails.

What makes this confusing is that, on a controller without [ApiController], a body that's too large doesn't produce an obvious error: the form can't be read, so the [FromForm] model comes through as null.

What I tested (.NET 9, Kestrel, same defaults as .NET 8)

I posted a multipart form with two text fields and one file to a [FromForm] DTO:

RequestController without [ApiController]Controller with [ApiController]5 MB fileAll values arriveAll values arrive5 MB fileAll values arriveAll values arrive35 MB fileThe whole [FromForm] model is null400: "Failed to read the request form. Request body too large. The max request body size is 30000000 bytes."1. Check whether this is your problem

In the JavaScript, log the size of what you're sending, just before fetch, on a failing and a working device:

const totalBytes = [...formData.values()]
    .reduce((sum, value) => sum + (value instanceof File ? value.size : 0), 0);
console.log(`Upload size: ${(totalBytes / 1_000_000).toFixed(1)} MB`);

On the server, stop the failure from being silent. Check the model and ModelState at the start of the action, and the error message tells you directly:

if (form is null || !ModelState.IsValid)
{
    var errors = ModelState.Values.SelectMany(v => v.Errors).Select(e => e.ErrorMessage);
    return BadRequest(errors); // e.g. "Request body too large. The max request body size is 30000000 bytes."
}

2. If that's it, raise the limit for this action

[HttpPost]
[RequestSizeLimit(100_000_000)] // 100 MB for this action only
public IActionResult Submit([FromForm] CustomerForm form) { ... }

In my test, the 35 MB request bound correctly with this attribute. If a single upload can exceed 128 MB, also add [RequestFormLimits(MultipartBodyLengthLimit = ...)].

When the app is hosted in IIS (which SmarterASP uses) or run under IIS Express, IIS request filtering has its own limit, so raise it in web.config as well:

<system.webServer>
  <security>
    <requestFiltering>
      <requestLimits maxAllowedContentLength="104857600" />
    </requestFiltering>
  </security>
</system.webServer>

Pick the smallest limit that covers your real uploads. Resizing or compressing photos in the browser before upload is often a better fix than accepting very large requests.

If the logged sizes on the failing iPhones are well under 28 MB, it's something else, and Nguyen's diagnostic endpoint, comparing Request.Form on both devices, is the right next step.

Let me know what sizes you see. If this solves it, please consider marking it as the accepted answer so others with the same problem can find it.

Paul Thomas 160 Reputation points

2026-10-29T12:47:50.5+00:00
@Ibrahim Akuetiemhe
Thanks for posting the diagnostics. They rule out the size limit I suggested: the affected iPhone sends a valid multipart Content-Type with a boundary, but contentLength is 0 with no fields or files. So the browser is sending an empty body, before ASP.NET Core does anything. Your server code and the fetch call look fine. You let the browser set the Content-Type, which is correct.

Since the text fields go missing too, not just the files, my guess is that Safari fails to read one of the attached files and ends up sending nothing. I can't reproduce this on iOS 27, so here are some quick tests on the affected iPhone to narrow it down:

Test 1. Submit the form with no files attached. If the text fields then arrive, the attached file is the trigger.

Test 2. Log what's in the FormData right before fetch:

for (const [key, value] of formData.entries()) { console.log(key, value instanceof File ? `${value.name} ${value.type} ${value.size} bytes` : value); }

Look for a file with 0 bytes, an unexpected type such as image/heic, or one picked from iCloud Photos (with "Optimize iPhone Storage" enabled, the full photo may not be on the device).

Test 3. Read each file into memory before sending. If Safari can't read a file, this fails with a visible error instead of an empty request:

async function toInMemoryFile(file) { const bytes = await file.arrayBuffer(); // throws if the file can't be read return new File([bytes], file.name, { type: file.type || "application/octet-stream" }); } // in buildPolicyFormData (make it async): const idFile = document.getElementById('idUpload')?.files[0]; if (idFile) formData.append("Identification", await toInMemoryFile(idFile));

If it doesn't throw, the in-memory copy may also fix the upload.

To see the exact request, connect the iPhone to a Mac and use Safari → Develop → [your iPhone] (Web Inspector). The Network tab shows the request body Safari sends.
Ibrahim Akuetiemhe 0 Reputation points

2026-10-29T13:35:56.2866667+00:00
the total upload size is 0.5MB while this code
if (b is null || !ModelState.IsValid)

{

var errors = ModelState.Values.SelectMany(v => v.Errors).Select(e => e.ErrorMessage); return BadRequest(errors); // e.g. "Request body too large. The max request body size is 30000000 bytes."

}

producess the response from the attached image
Paul Thomas 160 Reputation points

2026-10-29T18:11:45.5933333+00:00
@Ibrahim Akuetiemhe Thanks, that screenshot confirms it. 0.5 MB rules out a size limit, and every field fails validation: FirstName, LastName, EmailAddress, PhoneNumber, Covers, CoverFiles, and so on. "Sex must be between 1 and 2" means Sex stayed at its default of 0. So nothing was bound at all, which matches the contentLength: 0 you logged. Safari sends an empty body, and model binding has nothing to bind. The server side is working correctly.

The quickest way to narrow it down is still on the affected iPhone:

Test 1: submit with no files attached. Do the text fields arrive?

Test 3: wrap each file with toInMemoryFile() before appending it. Does it throw, or does the upload start working?

Those two results will show whether one of the selected files is what makes Safari drop the whole body.
Ibrahim Akuetiemhe 0 Reputation points

2026-11-12T06:16:35.5533333+00:00

Thank for the follow up. I will be replacing my laptop before the end of next week.

However, it seems it's working because the backend returned the payload as json serialise and the image information is included. You can test it too. demo.prudentchoice.com.ng
Paul Thomas 160 Reputation points

2026-11-12T07:11:01.48+00:00

@Ibrahim Akuetiemhe Great to hear it's working, thanks for testing it. Once you've confirmed it on the new laptop as well, please mark the answer as accepted so others who hit the same iPhone issue can find it.

Ibrahim Akuetiemhe 0

Good news.
It has worked.
I use this helper to fix it

async function appendMemoryFile(formData, fieldName, file) {

    if (!file) return;

    const buffer = await file.arrayBuffer();

    const memoryBlob = new Blob(

        [buffer],

        { type: file.type }

    );

    formData.append(fieldName, memoryBlob, file.name);

}

Answer 4

These are my code samples

**Controller
** public async Task<IActionResult> Get([FromForm] BuyInsuranceDTO b)

{

    //if (!User.HasClaim("Permission", Permissions.PurchasePolicy))

    //{

    //    return StatusCode(403, new

    //    {

    //        success = false,

    //        message = "Sorry, you cant purchase policy at the moment."

    //    });

    //}



    var loggedInCustomer = Convert.ToInt16(User.FindFirst(ClaimTypes.NameIdentifier)?.Value);

    var upload = Request.Form.Files.Where(x => x.Name == "Identification").FirstOrDefault();

    var createPolicy = await service.CreateService(b, upload, loggedInCustomer, User.Identity.IsAuthenticated);

    if (!createPolicy.Success)

    {

        return Json(new MyResponse { Success = false, Message = createPolicy.Message });

    }

    return Json(new MyResponse { Success = true, Message = createPolicy.Message });

}**

DTO
public class BuyInsuranceDTO**

**{**

    **// ================= BASIC =================**

    **[Required]**

    **public string FirstName { get; set; }**

    **[Required]**

    **public string LastName { get; set; }**

    **public string MiddleName { get; set; }**

    **[Required]**

    **[Range(1, 2)]**

    **public int Sex { get; set; }**

    **[Required]**

    **public DateTime DOB { get; set; }**

    **[Required]**

    **public string PhoneNumber { get; set; }**

    **[Required]**

    **public string Address { get; set; }**

    **public string EmailAddress { get; set; }**

    **public string Agent { get; set; }**

    **// ================= NEXT OF KIN =================**

    **[Required]**

    **public string NOKFullName { get; set; }**

    **public int NOKRelationship { get; set; }**

    **[Required]**

    **public string NOKPhoneNumber { get; set; }**

    **[Required]**

    **public string NOKAddress { get; set; }**

    **// ================= POLICY =================**

    **public Guid? PolicyID { get; set; }**

    **[Required]**

    **public List<CoverItemDTO> Covers { get; set; }**

    **// ================= IDENTIFICATION =================**

    **[Required]**

    **public int IdentificationTypeId { get; set; }**

    **[Required]**

    **public string IdentificationNumber { get; set; }**

    **public DateTime? ExpiryDate { get; set; }**

    **public IFormFile Identification { get; set; }**

    **// ================= BUSSINESS ADDRESS =================**

    **public string StreetNumber { get; set; }**

    **[Required]**

    **public string StreetName { get; set; }**

    **public string LandMark { get; set; }**

    **[Required]**

    **public int StateID { get; set; }**

    **[Required]**

    **public int LGAID { get; set; }**

    **[Required]**

    **public int AccountID { get; set; }**

    **// ================= COVER UPLOADS =================**

    **public List<CoverFileUploadDTO> CoverFiles { get; set; }**

    **//============ Declared Items=================**

    **public List<DeclarationItemsDTO> DeclarationItems { get; set; }**

**}**

Java Script
async function handleFinalSubmission() {

**if (!confirm('Are you sure you want to submit this policy application?')) {**

    **return;**

**}**

**const formData = buildPolicyFormData();**

**const result = await sendPolicy(formData);**

**if (!result) {**

    **return;**

**}**

**alert(result.message);**

**if (result.success) {**

    **window.location.href =**

        **'/policylisting/insuranceproduct';**

**}**

}

async function sendPolicy(formData) {

**if (isSubmitting) return;**

**isSubmitting = true;**

**showLoader();**

**try {**

    **const res = await fetch(`/policyListing/get`, {**

        **method: 'POST',**

        **body: formData**

    **});**

    **const data = await res.json();**

    **return data;**

**} catch (err) {**

    **console.error(err);**

    **alert("Failed to submit policy");**

    **return null;**

**} finally {**

    **isSubmitting = false;**

    **hideLoader();**

**}**

}

function appendIfExists(formData, key, elementId) {

const el = document.getElementById(elementId);

if (el)

    formData.append(key, el.value.trim());

}

function buildPolicyFormData() {

const formData = new FormData();

appendIfExists(formData, "FirstName", "firstName");

appendIfExists(formData, "MiddleName", "middleName");

appendIfExists(formData, "LastName", "lastName");

appendIfExists(formData, "PhoneNumber", "phone");

appendIfExists(formData, "Sex", "sex");

appendIfExists(formData, "DOB", "dob");

appendIfExists(formData, "Agent", "agent");

appendIfExists(formData, "Address", "address");

appendIfExists(formData, "EmailAddress", "email");

appendIfExists(formData, "NOKFullName", "nokName");

appendIfExists(formData, "NOKRelationship", "nokRelationship");

appendIfExists(formData, "NOKPhoneNumber", "nokPhone");

appendIfExists(formData, "NOKAddress", "nokAddress");

appendIfExists(formData, "IdentificationTypeId", "idType");

appendIfExists(formData, "IdentificationNumber", "idNumber");

appendIfExists(formData, "ExpiryDate", "expiryDate");

appendIfExists(formData, "StateID", "businessState");

appendIfExists(formData, "LGAID", "businessLga");

appendIfExists(formData, "StreetNumber", "businessStreetNumber");

appendIfExists(formData, "StreetName", "businessAddress");

appendIfExists(formData, "LandMark", "businessLandmark");

const idFile = document.getElementById('idUpload')?.files[0];

if (idFile) formData.append("Identification", idFile);

if (policyId) {

    formData.append("PolicyID", policyId);

}

// Covers

if (isCustomPolicy && selectedCovers.length > 0) {

    selectedCovers.forEach((cover, i) => {

        formData.append(`Covers[${i}].CoverID`, cover.CoverID);

        formData.append(`Covers[${i}].RiskCovered`, coverRisks[cover.CoverID] || 0);

    });

} else if (selectedCoverIds.length > 0) {

    selectedCoverIds.forEach((id, i) => {

        formData.append(`Covers[${i}].CoverID`, id);

    });

}

// Dynamic Cover Files

let fileIndex = 0;

let itemIndex = 0;

document.querySelectorAll('.cover-upload').forEach(input => {

    const file = input.files[0];

    if (file) {

        formData.append(`CoverFiles[${fileIndex}].File`, file);

        formData.append(`CoverFiles[${fileIndex}].CoverId`, input.dataset.coverid);

        formData.append(`CoverFiles[${fileIndex}].Label`, input.dataset.label);

        formData.append(`CoverFiles[${fileIndex}].coverUploadRequirementID`, input.name);

        fileIndex++;

    }

});

// Declaration Items

document.querySelectorAll("#tblDeclarationItems tbody tr").forEach(row => {

    const itemName = row.querySelector(".item-name")?.value.trim();

    const amount = row.querySelector(".item-amount")?.value;

    // Ignore empty rows

    if (!itemName || !amount)

        return;

    formData.append(`DeclarationItems[${itemIndex}].ItemName`, itemName);

    formData.append(`DeclarationItems[${itemIndex}].Amount`, amount);

    itemIndex++;

});

return formData;

}

Answer 5

This is from a working device
{

"contentType": "multipart/form-data; boundary=----WebKitFormBoundaryPgoBscBBF4qYl6KM",

"contentLength": 111491,

"fields": {

    "FirstName": {

        "count": 1,

        "hasValue": true

    },

    "MiddleName": {

        "count": 1,

        "hasValue": true

    },

    "LastName": {

        "count": 1,

        "hasValue": true

    },

    "PhoneNumber": {

        "count": 1,

        "hasValue": true

    },

    "Sex": {

        "count": 1,

        "hasValue": true

    },

    "DOB": {

        "count": 1,

        "hasValue": true

    },

    "Agent": {

        "count": 1,

        "hasValue": true

    },

    "Address": {

        "count": 1,

        "hasValue": true

    },

    "EmailAddress": {

        "count": 1,

        "hasValue": true

    },

    "NOKFullName": {

        "count": 1,

        "hasValue": true

    },

    "NOKRelationship": {

        "count": 1,

        "hasValue": true

    },

    "NOKPhoneNumber": {

        "count": 1,

        "hasValue": true

    },

    "NOKAddress": {

        "count": 1,

        "hasValue": true

    },

    "IdentificationTypeId": {

        "count": 1,

        "hasValue": true

    },

    "IdentificationNumber": {

        "count": 1,

        "hasValue": true

    },

    "ExpiryDate": {

        "count": 1,

        "hasValue": false

    },

    "StateID": {

        "count": 1,

        "hasValue": false

    },

    "LGAID": {

        "count": 1,

        "hasValue": false

    },

    "StreetNumber": {

        "count": 1,

        "hasValue": false

    },

    "StreetName": {

        "count": 1,

        "hasValue": false

    },

    "LandMark": {

        "count": 1,

        "hasValue": false

    },

    "PolicyID": {

        "count": 1,

        "hasValue": true

    },

    "Covers[0].CoverID": {

        "count": 1,

        "hasValue": true

    },

    "CoverFiles[0].CoverId": {

        "count": 1,

        "hasValue": true

    },

    "CoverFiles[0].Label": {

        "count": 1,

        "hasValue": true

    },

    "CoverFiles[0].coverUploadRequirementID": {

        "count": 1,

        "hasValue": true

    }

},

"files": [

    {

        "name": "Identification",

        "fileName": "NIA.png",

        "contentType": "image/png",

        "length": 54168

    },

    {

        "name": "CoverFiles[0].File",

        "fileName": "NIA.png",

        "contentType": "image/png",

        "length": 54168

    }

],

"totalFields": 26,

"totalFiles": 2

}

And this is from the iPhone
{

"contentType": "multipart/form-data; boundary=----WebKitFormBoundaryqXbmvYh367BCwgcB",

"contentLength": 0,

"fields": 0,

"files": 0,

"totalFields": 0,

"totalFiles": 0

}

ASP.NET Core .NET 8 receives null form values from certain iPhone 13 Pro Max devices

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