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When errors occur during the execution of a SQL Server Compact 3.5-based application, the OLE DB provider for SQL Server Compact 3.5 returns and stores an array of error objects. These objects can then be accessed using OLE DB in the typical manner. The OLE DB provider for SQL Server Compact 3.5 returns errors for each interface supported by the provider. For more information, see Implemented OLE DB Interfaces (SQL Server Compact). For information about the general mechanism for an OLE DB client to retrieve error information, see the Microsoft OLE DB section of the Microsoft Data Access Components (MDAC) SDK documentation in the MSDN Library.

The following example shows how to retrieve the provider-specific error numbers when you use the OLE DB provider for SQL Server Compact 3.5.

In order for this example application to run the sqlceoledb35.dll must be registered. The sqlceoledb35.dll can be registered in Windows from a command line with the regsvr32 utility.

CLSID_SQLSERVERCE is a macro defined in the OLEDB header file that maps to CLSID_SQLSERVERCE_3_5.

#include <windows.h>
#include <sqlce_oledb.h>
#include <sqlce_err.h>
#include <stdio.h>

/// <summary>
/// This function demonstrates a routine that can handle and display 
/// errors from the OLE DB provider for SQL Server Compact 3.5. The
/// errors that occured on the current thread are displayed.
/// </summary>

HRESULT DisplayCurrentThreadErrors()
{
    static TCHAR *sErrIErrorInfo     = L"IErrorInfo interface";
    static TCHAR *sErrIErrorRecords  = L"IErrorRecords interface";
    static TCHAR *sErrRecordCount    = L"error record count";
    static TCHAR *sErrInfo           = L"ERRORINFO structure";
    static TCHAR *sErrStandardInfo   = L"standard error info";
    static TCHAR *sErrDescription    = L"standard error description";
    static TCHAR *sErrNoSource       = L"error source";

    HRESULT hr                          = S_OK;
    IErrorInfo       *pIErrorInfo       = NULL;
    IErrorRecords    *pIErrorRecords    = NULL;
    ERRORINFO        errorInfo          = { 0 };
    IErrorInfo       *pIErrorInfoRecord = NULL;

    try
    {
        // This interface supports returning error information.
        // Get the error object from the system for the current
        // thread.
        hr = GetErrorInfo(0, &pIErrorInfo);
        if ( hr == S_FALSE )
        {
            wprintf(L"No error occured.\n");
            return S_OK;
        }

        if(FAILED(hr) || NULL == pIErrorInfo)
            throw sErrIErrorInfo;

        // The error records are retrieved from the IIErrorRecords
        // interface, which can be obtained from the IErrorInfo
        // interface.
        hr = pIErrorInfo->QueryInterface(IID_IErrorRecords,
            (void **) &pIErrorRecords);
        if ( FAILED(hr) || NULL == pIErrorRecords )
            throw sErrIErrorRecords;

        // The IErrorInfo interface is no longer required because
        // we have the IErrorRecords interface, relase it.
        pIErrorInfo->Release();
        pIErrorInfo = NULL;

        ULONG ulNumErrorRecs = 0;

        // Determine the number of records in this error object
        hr = pIErrorRecords->GetRecordCount(&ulNumErrorRecs);
        if ( FAILED(hr) )
            throw sErrRecordCount;


        // Loop over each error record in the error object to display 
        // information about each error. Errors are returned. 
        for (DWORD dwErrorIndex = 0;
             dwErrorIndex < ulNumErrorRecs;
             dwErrorIndex++)
        {
            // Retrieve basic error information for this error.
            hr = pIErrorRecords->GetBasicErrorInfo(dwErrorIndex,
              &errorInfo);
            if ( FAILED(hr) )
                throw sErrInfo;

            TCHAR szCLSID[64]  = { 0 };
            TCHAR szIID[64]    = { 0 };
            TCHAR szDISPID[64] = { 0 };

            StringFromGUID2(errorInfo.clsid, (LPOLESTR)szCLSID,
                sizeof(szCLSID));
            StringFromGUID2(errorInfo.iid, (LPOLESTR)szIID,
                sizeof(szIID));

            wprintf(L"HRESULT           = %lx\n", errorInfo.hrError);
            wprintf(L"clsid             = %s\n", szCLSID);
            wprintf(L"iid               = %s\n", szIID);
            wprintf(L"dispid            = %ld\n", errorInfo.dispid);
            wprintf(L"Native Error Code = %lx\n", errorInfo.dwMinor);

            // Retrieve standard error information for this error.
            hr = pIErrorRecords->GetErrorInfo(dwErrorIndex, NULL,
                &pIErrorInfoRecord);

            if ( FAILED(hr) )
                throw sErrStandardInfo;

            BSTR bstrDescriptionOfError;
            BSTR bstrSourceOfError;

            // Get the description of the error.
            hr = pIErrorInfoRecord->GetDescription(
                   &bstrDescriptionOfError);
            if ( FAILED(hr) )
                throw sErrDescription;

            wprintf(L"Description = %s\n", bstrDescriptionOfError);

            // Get the source of the error.
            hr = pIErrorInfoRecord->GetSource(&bstrSourceOfError);
            if ( FAILED(hr) )
                throw sErrNoSource;

            wprintf(L"Description = %s\n", bstrSourceOfError);

            // This interface variable will be used the next time 
            // though this loop. In the last error case this interface 
            // is no longer needed so we must release it.
            if(NULL != pIErrorInfoRecord)
                pIErrorInfoRecord->Release();
            pIErrorInfoRecord = NULL;
        }
    }
    catch( TCHAR *szMsg )
    {
        wprintf(L"Failed to retrieve ");
        wprintf(szMsg);
    }

    if( pIErrorInfoRecord )
        pIErrorInfoRecord->Release();

    if ( pIErrorInfo )
        pIErrorInfo->Release();

    if ( pIErrorRecords )
        pIErrorRecords->Release();

    return hr;
}

/// <summary>
/// This called will try to connect to a non existant
/// database to cause an error condition so that the call
/// to DisplayCurrentThreadError() has some errors to
/// display.
/// </summary>
/// <param="pIDBProperties">
/// IDBProperties interface that is used to set the properties on
/// for the Sql Compact engine object.
/// </param>
/// <param="pIDBInitialize">
/// Interface to the Sql Compact initialization object.
/// </param>

void CreateErrorCondition(IDBProperties *pIDBProperties,
                          IDBInitialize *pIDBInitialize)
{
    HRESULT     hr = S_OK;
    DBPROP      dbprop[1];
    DBPROPSET   dbpropset[1];

    VariantInit(&dbprop[0].vValue);

    // Initialize a property that uses name of database.
    dbprop[0].dwPropertyID   = DBPROP_INIT_DATASOURCE;
    dbprop[0].dwOptions      = DBPROPOPTIONS_REQUIRED;
    dbprop[0].vValue.vt      = VT_BSTR;
    dbprop[0].vValue.bstrVal = SysAllocString(L"t@#$94.SC5");

    // Initialize the property set.
    dbpropset[0].guidPropertySet = DBPROPSET_DBINIT;
    dbpropset[0].rgProperties    = dbprop;
    dbpropset[0].cProperties     = sizeof(dbprop)/sizeof(dbprop[0]);

    hr = pIDBProperties->SetProperties(
          sizeof(dbpropset)/sizeof(dbpropset[0]),
          dbpropset);
    VariantClear(&dbprop[0].vValue);

    if( FAILED(hr) )
        return;

    SysFreeString(dbprop[0].vValue.bstrVal);

    // This call will fail because the db does not exit.
    pIDBInitialize->Initialize();
}

/// <summary>
/// Application entry point initializes and cleans up the
/// needed interfaces and then calls the
/// DisplayCurrentThreadErrors() function to display error
/// information for the main application thread.
/// </summary>

void main()
{
    HRESULT hr                            = S_OK;
    IDBProperties     *pIDBProperties     = NULL;
    ISupportErrorInfo *pISupportErrorInfo = NULL;
    IDBInitialize     *pIDBInitialize     = NULL;
    BOOL bComInitialized                  = FALSE;

    try
    {
        hr = CoInitialize(NULL);
        if ( FAILED(hr) )
        {
            wprintf(L"CoInitialize failed");
            throw hr;
        }

        bComInitialized = TRUE;

        // Retrieve the SQL Compact edition initialization interface.
        hr = CoCreateInstance(CLSID_SQLSERVERCE,
                0,
                CLSCTX_INPROC_SERVER,
                IID_IDBInitialize,
                (void**)&pIDBInitialize);
        if( FAILED(hr) || NULL == pIDBInitialize )
        {
            wprintf(L"Failed to retrieve IDBInitialize Interface");
            throw hr;
        }

        // Retrieve the property interface, This interface will enable
        // setting of specific propertes on the SQL Server Compact
        //  engine object.
        hr = CoCreateInstance(CLSID_SQLSERVERCE,
            0,
            CLSCTX_INPROC_SERVER,
            IID_IDBProperties,
            (void**) &pIDBProperties);

        if( FAILED(hr) || NULL == pIDBProperties )
        {
            wprintf(L"Failed to retrieve IDBProperties Interface");
            throw hr;
        }

        hr = pIDBProperties->QueryInterface(IID_ISupportErrorInfo,
            (void**)&pISupportErrorInfo);

        if( FAILED(hr) || NULL == pISupportErrorInfo )
        {
            wprintf(L"Interface does not support ISupportErrorInfo");
            throw hr;
        }

        // Create an error condition by trying to open a non existance
        // datafile.
        CreateErrorCondition(pIDBProperties, pIDBInitialize);

        // Display errors that occured on the current (main) thread.
        hr = DisplayCurrentThreadErrors();
        if ( FAILED(hr) )
            throw hr;
    }
    catch( HRESULT hr)
    {
        wprintf(L", Error Code: %lx\n", hr);
    }

    if ( pISupportErrorInfo )
        pISupportErrorInfo->Release();

    if ( pIDBProperties )
        pIDBProperties->Release();

    if ( pIDBInitialize )
        pIDBInitialize->Release();

    if ( bComInitialized )
        CoUninitialize();
}
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