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copied!<p>You should be setting a DBBINDING that includes DBPART_LENGTH to get the length of the field. To illustrate this, I've created some VARCHAR data in SQL Server using the following DDL:</p> <pre><code>CREATE TABLE NEWS ( ID INT NOT NULL, ARTICLE NVARCHAR(4000) ); INSERT INTO NEWS (1, 'Today is a sunny day.'); </code></pre> <p>Then I use the following ATL based C++ code sample to read the ARTICLE field. If you put breakpoints in the code, you will see it will come back with</p> <ul> <li>data.nArticleLength = 21</li> <li>data.szArticle = "Today is a sunny day."</li> </ul> <p>Here's the code sample sample:</p> <pre><code>#include <stdio.h> #include <tchar.h> #include <windows.h> #include <oledb.h> #include <atlbase.h> int _tmain(int argc, _TCHAR* argv[]) { HRESULT hr = S_OK; hr = CoInitializeEx(NULL, COINIT_MULTITHREADED); // Connect to SQL Server. CComPtr<IDBInitialize> spIDBInitialize; hr = spIDBInitialize.CoCreateInstance(OLESTR("SQLNCLI")); CComPtr<IDBProperties> spIDBProperties; hr = spIDBInitialize->QueryInterface(IID_IDBProperties, (void**) &spIDBProperties); CComVariant varDataSource(OLESTR("InsertYourSQLServer")); CComVariant varCatalog(_T("InsertYourDatabase")); CComVariant varUserID(_T("InsertYourUserName")); CComVariant varPassword(_T("InsertYourPassword")); DBPROP rgProps[4] = { { DBPROP_INIT_DATASOURCE, DBPROPOPTIONS_REQUIRED, 0, DB_NULLID, varDataSource }, { DBPROP_INIT_CATALOG, DBPROPOPTIONS_REQUIRED, 0, DB_NULLID, varCatalog }, { DBPROP_AUTH_USERID, DBPROPOPTIONS_REQUIRED, 0, DB_NULLID, varUserID }, { DBPROP_AUTH_PASSWORD, DBPROPOPTIONS_REQUIRED, 0, DB_NULLID, varPassword } }; DBPROPSET propSet = {rgProps, 4, DBPROPSET_DBINIT}; hr = spIDBProperties->SetProperties(1, &propSet); spIDBProperties = NULL; hr = spIDBInitialize->Initialize(); // Execute the query. CComPtr<IDBCreateSession> spIDBCreateSession; hr = spIDBInitialize->QueryInterface(IID_IDBCreateSession, (void**) &spIDBCreateSession); CComPtr<IDBCreateCommand> spIDBCreateCommand; hr = spIDBCreateSession->CreateSession(NULL, IID_IDBCreateCommand, (IUnknown**) &spIDBCreateCommand); spIDBCreateSession = NULL; CComPtr<ICommandText> spICommandText; hr = spIDBCreateCommand->CreateCommand(NULL, IID_ICommandText, (IUnknown**) &spICommandText); spIDBCreateCommand = NULL; hr = spICommandText->SetCommandText(DBGUID_SQL, OLESTR("SELECT ID, ARTICLE FROM NEWS")); DBROWCOUNT cRowsAffected = 0; CComPtr<IRowset> spIRowset; hr = spICommandText->Execute(NULL, IID_IRowset, NULL, &cRowsAffected, (IUnknown**) &spIRowset); spICommandText = NULL; // Retrieve records. HROW hRow = NULL; HROW *rghRow = &hRow; DBCOUNTITEM cRowsObtained = 0; hr = spIRowset->GetNextRows(DB_NULL_HCHAPTER, 0, 1, &cRowsObtained, &rghRow); while (hr == S_OK && cRowsObtained == 1) { // Fetch the ARTICLE field. struct { DBSTATUS dbArticleStatus; ULONG nArticleLength; char szArticle[4000 + 4]; } data = {0}; DBBINDING Binding = {0}; Binding.iOrdinal = 2; Binding.obValue = sizeof(DBSTATUS) + sizeof(ULONG); Binding.obLength = sizeof(DBSTATUS); Binding.obStatus = 0; Binding.pTypeInfo = NULL; Binding.pObject = NULL; Binding.pBindExt = NULL; Binding.dwPart = DBPART_STATUS | DBPART_LENGTH | DBPART_VALUE; Binding.dwMemOwner = DBMEMOWNER_CLIENTOWNED; Binding.eParamIO = DBPARAMIO_NOTPARAM; Binding.cbMaxLen = 4000 + 1; Binding.wType = DBTYPE_STR; Binding.dwFlags = 0; Binding.bPrecision = 0; Binding.bScale = 0; CComPtr<IAccessor> spIAccessor; hr = spIRowset->QueryInterface(IID_IAccessor, (void**) &spIAccessor); HACCESSOR hAccessor = NULL; hr = spIAccessor->CreateAccessor(DBACCESSOR_ROWDATA, 1, &Binding, 0, &hAccessor, NULL); hr = spIRowset->GetData(hRow, hAccessor, &data); DBREFCOUNT cRefCount = 0; hr = spIAccessor->ReleaseAccessor(hAccessor, &cRefCount); spIAccessor = NULL; // @@TODO: Do something with data.szArticle and data.nArticleLength // ... // Fetch next row of data. hr = spIRowset->ReleaseRows(1, rghRow, NULL, NULL, NULL); cRowsObtained = 0; hr = spIRowset->GetNextRows(DB_NULL_HCHAPTER, 0, 1, &cRowsObtained, &rghRow); } // Release everything spIRowset = NULL; spIDBInitialize = NULL; CoUninitialize(); return 0; } </code></pre>

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