Get the Content-ID of an Attachment

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Demonstrates the Chilkat Email.GetAttachmentContentID method, which returns the Content-ID header field for the Nth attachment. The index is zero-based, so the first attachment is 0. This example adds an attachment and reads its Content-ID (which may be empty when none was assigned).

Background: A Content-ID is a unique identifier for a MIME part. It is essential for inline "related" resources, where HTML references an image by cid:, but ordinary file attachments usually have none. Reading it is useful when inspecting how a message is assembled, or when distinguishing parts that are referenced from the body versus those meant purely as downloadable attachments.

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#include <C_CkEmail.h>

void ChilkatSample(void)
    {
    HCkEmail email;
    const char *cid;

    //  Demonstrates the GetAttachmentContentID method, which returns the Content-ID header
    //  field for the Nth attachment.  The index is zero-based (the first attachment is 0).

    email = CkEmail_Create();
    CkEmail_putSubject(email,"Attachment Content-ID");

    CkEmail_AddStringAttachment(email,"notes.txt","Some notes.");

    //  Get the Content-ID of the first attachment (may be empty if none was assigned).
    cid = CkEmail_getAttachmentContentID(email,0);
    printf("Attachment 0 Content-ID: %s\n",cid);


    CkEmail_Dispose(email);

    }