CertGetNameString (crypt32)
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The CertGetNameString function obtains the subject or issuer name from a certificate CERT_CONTEXT structure and converts it to a null-terminated character string.

C# Signature:

[DllImport("crypt32.dll", EntryPoint = "CertGetNameString", CharSet = CharSet.Auto, SetLastError = true)]
static extern UInt32 CertGetNameString(IntPtr CertContext, UInt32 lType, UInt32 lFlags, IntPtr pTypeParameter, System.Text.StringBuilder str, UInt32 cch);

VB Signature:

Declare Function CertGetNameString Lib "Crypt32.dll" Alias "CertGetNameStringW" ( _
    ByVal pCertContext As Long, _
    ByVal dwType As Long, _
    ByVal dwFlags As Long, _
    pvTypePara As Any, _
    ByVal pszNameString As Long, _
    ByVal cchNameString As Long _
    ) As Long

User-Defined Types:

    const uint CERT_NAME_EMAIL_TYPE         = 1;
    const uint CERT_NAME_RDN_TYPE           = 2;
    const uint CERT_NAME_ATTR_TYPE          = 3;
    const uint CERT_NAME_SIMPLE_DISPLAY_TYPE    = 4;
    const uint CERT_NAME_DNS_TYPE           = 6;
    const uint CERT_NAME_URL_TYPE           = 7;
    const uint CERT_NAME_UPN_TYPE           = 8;

    const uint CERT_NAME_ISSUER_FLAG        = 0x1;
    const uint CERT_NAME_DISABLE_IE4_UTF8_FLAG  = 0x00010000;

Alternative Managed API:

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For VB usage:

Ensure you use StrPtr and that the function signature is "CertGetNameStringW", or you will regularly crash your program!

Tips & Tricks:

You can call this first with a null buffer and null cchNameString to return just the required buffer length, then size the buffer appropriately and call again as above!

Sample Code:


        while ((certContext = CertEnumCertificatesInStore(hCertStore, certContext)) != IntPtr.Zero)
        StringBuilder Buffer = new StringBuilder(255);
        UInt32 cchString = 255 ;
        System.UInt32 nChars = CertGetNameString(certContext,
        // use Buffer.ToString() to use the cert's name string


     Dim bfr As String, bPtr As Long
     bfr = String(szNameString, vbNullChar)
     bPtr = StrPtr(bfr)
     szNameString = CertGetNameString(hCert_Context&, _
                      CERT_NAME_SIMPLE_DISPLAY_TYPE, _
                      0&, _
                      0&, _
                      bPtr&, _
128& _                      )