Sharepoint API creating folder 403

Question

I am new to the SharePoint API. I am trying to create folders in a customer SharePoint solution.

Problem is i'm getting a 403 return. My request.:

POST https://companyname.sharepoint.com/sites/Test/_api/Web/GetFolderByServerRelativePath(decodedurl='/sites/Test/Syra_Test') HTTP/1.1
X-FORMS_BASED_AUTH_ACCEPTED: f
X-RequestDigest:xxxxxxx,28 Apr 2021 10:03:46 -0000
X-HTTP-Method: POST
Cookie: SPOIDCRL=xxxxxxxx
Authorization: 
Host: companyname.sharepoint.com
Content-Length: 69
Expect: 100-continue

{'__metadata': {'type':'SP.Folder'},'ServerRelativeUrl': '/syraHest'}

My response.:

<?xml version="1.0" encoding="utf-8"?><m:error xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"><m:code>-2130575251, System.Runtime.InteropServices.COMException</m:code><m:message xml:lang="en-US">The security validation for this page is invalid. Click Back in your Web browser, refresh the page, and try your operation again.</m:message></m:error>

Here is my code.:

WebClient client = new WebClient();

            string USER = "[email protected]";
            SecureString passWord = new SecureString();
            string PWD = "xxxxxxxx";
            PWD.ToList().ForEach(passWord.AppendChar);
            SharePointOnlineCredentials credentials = new SharePointOnlineCredentials(USER, passWord);
            client.Headers.Add("X-FORMS_BASED_AUTH_ACCEPTED", "f");
            client.Credentials = credentials;
            client.Headers.Add(HttpRequestHeader.ContentType, "application/json;odata=verbose");
            client.Headers.Add(HttpRequestHeader.Accept, "application/json;odata=verbose");
            client.BaseAddress = "https://companyname.sharepoint.com/sites/Test";
            // Get Digest
            string digestUrl = "/_api/contextinfo";
            string digestResult = client.UploadString(digestUrl, "POST");
            JToken dr = JToken.Parse(digestResult);
            string digest = dr["d"]["GetContextWebInformation"]["FormDigestValue"].ToString();

            // So far so good! FormDigest is returned here so I know I have correct credentials
            // Add Digest to next request
            client.BaseAddress = "https://companyname.sharepoint.com";
            client.Headers.Add("X-RequestDigest", digest);
            client.Headers.Add("X-HTTP-Method", "POST");                                          
            string endpointUri = "/sites/Test/_api/Web/GetFolderByServerRelativePath(decodedurl='/sites/Test/Syra_Test')/Folders"; 
            string payloadString = "{'__metadata': {'type':'SP.Folder'},'ServerRelativeUrl': '/syraHest'}";                         
            // Fails here 403!!
            string result = client.UploadString(endpointUri, "POST", payloadString);         
            //string result = client.DownloadString(endpointUri);
            JToken t = JToken.Parse(result);
            Console.WriteLine(t);

GET folders and the like works fine, so what am i missing in my POST requests ?

Edited code same result unfortunately.:

SharePointOnlineCredentials credentials = new SharePointOnlineCredentials(USER, passWord);
            client.Headers.Add("X-FORMS_BASED_AUTH_ACCEPTED", "f");
            client.Credentials = credentials;
            client.Headers.Add(HttpRequestHeader.ContentType, "application/json;odata=verbose");
            client.Headers.Add(HttpRequestHeader.Accept, "application/json;odata=verbose");
            client.BaseAddress = "https://companyname.sharepoint.com";
            // Get Digest
            string digestUrl = "/_api/contextinfo";
            string digestResult = client.UploadString(digestUrl, "POST");
            JToken dr = JToken.Parse(digestResult);
            string digest = dr["d"]["GetContextWebInformation"]["FormDigestValue"].ToString();
            // So far so good! FormDigest is returned here so I know I have correct credentials
            // Add Digest to next request            
            client.Headers.Add("X-RequestDigest", digest);
            client.Headers.Add("X-HTTP-Method", "POST");
            string endpointUri = "/sites/Test/_api/Web/folders";
            string payloadString = "{'__metadata': {'type':'SP.Folder'},'ServerRelativeUrl': '/sites/Test/Syra_Test/syraHest'}";
            // Fails here!!
            string result = client.UploadString(endpointUri, "POST", payloadString);           
            JToken t = JToken.Parse(result);
            Console.WriteLine(t);

Edit.: same error but new message.: 403 Access denied. You do not have permission to perform this action or access this resource

request.:

POST https://companyname.sharepoint.com/sites/Test/_api/Web/folders HTTP/1.1
X-RequestDigest: xxxxxxxx,29 Apr 2021 12:16:23 -0000
Accept: application/json;odata=verbose
Content-Type: application/json;odata=verbose
Host: companyname.sharepoint.com
Content-Length: 90
Expect: 100-continue
Connection: Keep-Alive

{'__metadata': {'type':'SP.Folder'},'ServerRelativeUrl': '/sites/Test/Syra_Test/syraHest'}

Answer 1

You can find the documentation on working with folders using the REST API here: https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/working-with-folders-and-files-with-rest

According to the documentation the POST to create a folder is:

POST https://{site_url}/_api/web/folders
Authorization: "Bearer " + accessToken
Accept: "application/json;odata=verbose"
Content-Type: "application/json"
Content-Length: {length of request body as integer}
X-RequestDigest: "{form_digest_value}"

{
  "__metadata": {
    "type": "SP.Folder"
  },
  "ServerRelativeUrl": "/document library relative url/folder name"
}

With that in mind changing your code to the following should solve your issue:

client.BaseAddress = "https://companyname.sharepoint.com";
client.Headers.Add("X-RequestDigest", digest);
client.Headers.Add("X-HTTP-Method", "POST");     
client.Headers.Add(HttpRequestHeader.ContentType, "application/json;odata=verbose");
client.Headers.Add(HttpRequestHeader.Accept, "application/json;odata=verbose");                                     
string endpointUri = "/sites/Test/_api/Web/folders"; 
string payloadString = "{'__metadata': {'type':'SP.Folder'},'ServerRelativeUrl': '/sites/Test/Syra_Test/syraHest'}";                         
string result = client.UploadString(endpointUri, "POST", payloadString);                                
JToken t = JToken.Parse(result);
Console.WriteLine(t);

The last time I checked, this code only creates the folder. It does not create the list item that is associated with the folder. I discuss alternative code you can use to create both the folder and the associated list item in this blog post: SharePoint REST API and Lists with Folders.