Get the Content-ID of a Related Item

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Demonstrates the Chilkat Email.GetRelatedContentID method, which returns the Content-ID of a related item (typically an image or style sheet embedded within an HTML email). The index is zero-based. This example loads an image from a file into a BinData object, adds it as a related item with AddRelatedBd (capturing the generated Content-ID and referencing it from the HTML), then reads that Content-ID back.

Background: The Content-ID is the anchor that ties an inline resource to the HTML that displays it: the body references cid: plus the ID, and the matching related part carries that same Content-ID. Because an image is binary, it is loaded into a BinData object (here from a file) and added with AddRelatedBd. Reading the Content-ID back lets a program verify or rewrite those links — for example when relocating embedded images or converting a message for display outside a mail client.

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#include <C_CkEmail.h>
#include <C_CkBinData.h>
#include <C_CkStringBuilder.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkEmail email;
    HCkBinData bdImage;
    const char *cid;
    HCkStringBuilder sbHtml;
    int numReplaced;
    const char *cid0;

    success = FALSE;

    //  Demonstrates the GetRelatedContentID method, which returns the Content-ID of a related
    //  item.  Related items are typically images and style sheets embedded within HTML emails.
    //  The index is zero-based.

    email = CkEmail_Create();
    CkEmail_putSubject(email,"GetRelatedContentID example");

    //  Load the image data from a file into a BinData object.
    bdImage = CkBinData_Create();
    success = CkBinData_LoadFile(bdImage,"qa_data/images/logo.png");
    if (success == FALSE) {
        printf("%s\n",CkBinData_lastErrorText(bdImage));
        CkEmail_Dispose(email);
        CkBinData_Dispose(bdImage);
        return;
    }

    //  Add the image as a related item from the BinData; capture its generated Content-ID.
    cid = CkEmail_addRelatedBd(email,"logo.png",bdImage);
    if (CkEmail_getLastMethodSuccess(email) == FALSE) {
        printf("%s\n",CkEmail_lastErrorText(email));
        CkEmail_Dispose(email);
        CkBinData_Dispose(bdImage);
        return;
    }

    //  Reference the related item in the HTML body by its Content-ID.
    sbHtml = CkStringBuilder_Create();
    CkStringBuilder_Append(sbHtml,"<html><body><img src=\"cid:PLACEHOLDER_CID\"/></body></html>");
    numReplaced = CkStringBuilder_Replace(sbHtml,"PLACEHOLDER_CID",cid);
    CkEmail_SetHtmlBody(email,CkStringBuilder_getAsString(sbHtml));

    //  Read the Content-ID of the first related item (index 0).
    cid0 = CkEmail_getRelatedContentID(email,0);
    printf("Related item 0 Content-ID: %s\n",cid0);

    //  Note: The path "qa_data/images/logo.png" is a relative local filesystem path,
    //  relative to the current working directory of the running application.


    CkEmail_Dispose(email);
    CkBinData_Dispose(bdImage);
    CkStringBuilder_Dispose(sbHtml);

    }