(Delphi ActiveX) SharePoint -- Get Server Form Digest Value

Demonstrates how to get a server form digest value to be placed in the X-RequestDigest HTTP request header for POST, PUT, MERGE, and DELETE requests. A form digest value is typically valid for 1800 seconds (i.e. 30 minutes). This example persists the value to a file, and only requests a new form digest value if the existing one is near expiration.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
fac: TCkFileAccess;
xml: TChilkatXml;
success: Integer;
dtExpire: TCkDateTime;
dtNow: TCkDateTime;
formDigestXmlFile: WideString;
tNow: Integer;
tExpire: Integer;
http: TChilkatHttp;
savedAccept: WideString;
resp: IChilkatHttpResponse;
xml2: TChilkatXml;
timeoutInSec: Integer;

begin
// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// First, let's see if we already have a persisted form digest value
// that hasn't yet expired.
fac := TCkFileAccess.Create(Self);
xml := TChilkatXml.Create(Self);

// My example code (below) persists the form digest XML in this format:
// 
// 	<savedFormDigestValue>
// 	<d:ExpireDateTime>2017-04-12T20:46:39Z</d:ExpireDateTime>
// 	<d:FormDigestValue>0x3059FFB920651834540F3E6792EA73F5746B302E953FF4E808E485DB1E6C2836C7CF924644995F092453B02A94DE14A7962674B7B16780AF16EAFB8C246BCDC7,12 Apr 2017 17:08:22 -0000</d:FormDigestValue>
// 	</savedFormDigestValue>
// 

dtExpire := TCkDateTime.Create(Self);
dtNow := TCkDateTime.Create(Self);

formDigestXmlFile := 'qa_data/sharepoint/savedFormDigestValue.xml';
if (fac.FileExists(formDigestXmlFile) = 1) then
  begin

    xml.LoadXmlFile(formDigestXmlFile);

    // Get the expire date/time
    dtExpire.SetFromTimestamp(xml.GetChildContent('d:ExpireDateTime'));

    // Get the current date/time
    dtNow.SetFromCurrentSystemTime();

    // Get both times as Unix time values
    tNow := dtNow.GetAsUnixTime(0);
    tExpire := dtExpire.GetAsUnixTime(0);

    // If tNow >= tExpire, then fall through.
    // Otherwise, just use the cached digest value.
    if (tNow < tExpire) then
      begin
        Memo1.Lines.Add('Cached digest value is not yet expired.');
        Memo1.Lines.Add('X-RequestDigest: ' + xml.GetChildContent('d:FormDigestValue'));
        Exit;
      end;

  end;

// If we got to this point, the cached digest value either does not exist, or expired.

http := TChilkatHttp.Create(Self);

// If SharePoint Windows classic authentication is used, then set the 
// Login, Password, LoginDomain, and NtlmAuth properties.
http.Login := 'SHAREPOINT_USERNAME';
http.Password := 'SHAREPOINT_PASSWORD';
http.LoginDomain := 'SHAREPOINT_NTLM_DOMAIN';
http.NtlmAuth := 1;

// The more common case is to use SharePoint Online authentication (via the SPOIDCRL cookie).
// If so, do not set Login, Password, LoginDomain, and NtlmAuth, and instead
// establish the cookie as shown at SharePoint Online Authentication

// When creating, updating, and deleting SharePoint entities, we'll need
// to first get the server's form digest value to send in the X-RequestDigest header.
// This can be retrieved by making a POST request with an empty body to
// http://<site url>/_api/contextinfo and extracting the value of the
// d:FormDigestValue node in the XML that the contextinfo endpoint returns.

// Apparently, SharePoint needs an "Accept" request header equal to "application/xml",
// otherwise SharePoint will return an utterly incomprehensible and useless error message.
savedAccept := http.Accept;
http.Accept := 'application/xml';

// Note: The last argument ("utf-8") is meaningless here because the body is empty.
resp := http.PostXml('https://SHAREPOINT_HTTPS_DOMAIN/_api/contextinfo','','utf-8');
if (http.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

// Restore the default Accept header
http.Accept := savedAccept;

if (resp.StatusCode <> 200) then
  begin
    // A response status code not equal to 200 indicates failure.
    Memo1.Lines.Add('Response status code = ' + IntToStr(resp.StatusCode));
    Memo1.Lines.Add('Response body:');
    Memo1.Lines.Add(resp.BodyStr);

    Exit;
  end;

xml.LoadXml(resp.BodyStr);

// The response XML looks like this:

// <?xml version="1.0" encoding="utf-8" ?>
// <d:GetContextWebInformation xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns:georss="http://www.georss.org/georss" xmlns:gml="http://www.opengis.net/gml" m:type="SP.ContextWebInformation">
//     <d:FormDigestTimeoutSeconds m:type="Edm.Int32">1800</d:FormDigestTimeoutSeconds>
//     <d:FormDigestValue>0x3059FFB920651834540F3E6792EA73F5746B302E953FF4E808E485DB1E6C2836C7CF924644995F092453B02A94DE14A7962674B7B16780AF16EAFB8C246BCDC7,12 Apr 2017 17:08:22 -0000</d:FormDigestValue>
//     <d:LibraryVersion>15.0.4569.1000</d:LibraryVersion>
//     <d:SiteFullUrl>https://SHAREPOINT_HTTPS_DOMAIN</d:SiteFullUrl>
//     <d:SupportedSchemaVersions m:type="Collection(Edm.String)">
//         <d:element>14.0.0.0</d:element>
//         <d:element>15.0.0.0</d:element>
//     </d:SupportedSchemaVersions>
//     <d:WebFullUrl>https://SHAREPOINT_HTTPS_DOMAIN</d:WebFullUrl>
// </d:GetContextWebInformation>
// 

// Cache the digest value, and also an expiration time.  If this code is run again
// before the digest expires, we'll just get it from the file.
xml2 := TChilkatXml.Create(Self);

xml2.Tag := 'savedFormDigestValue';
xml2.NewChild2('d:FormDigestValue',xml.GetChildContent('d:FormDigestValue'));

timeoutInSec := xml.GetChildIntValue('d:FormDigestTimeoutSeconds');
Memo1.Lines.Add('Timeout in seconds = ' + IntToStr(timeoutInSec));

// Convert this to an expire timestamp.
// Let's make it expire 30 seconds prior to the actual timeout, just to be safe.
if (timeoutInSec > 30) then
  begin
    timeoutInSec := timeoutInSec - 30;
  end;

dtExpire.SetFromCurrentSystemTime();
dtExpire.AddSeconds(timeoutInSec);
xml2.NewChild2('d:ExpireDateTime',dtExpire.GetAsTimestamp(0));

// Persist the digest and expire time to a file.
xml2.SaveXml(formDigestXmlFile);

Memo1.Lines.Add('Here is the new form digest value:');
Memo1.Lines.Add('X-RequestDigest: ' + xml.GetChildContent('d:FormDigestValue'));
end;