GetString 方法示例 (VC++)

此示例演示 GetString 方法。

假设你正在调试数据访问问题，并且需要一种快速、简单的方法来打印小型 Recordset 的当前内容。

示例

// BeginGetString.cpp  
// compile with: /EHsc /c  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  
  
#include <ole2.h>  
#include <stdio.h>  
#include <conio.h>  
#include <string.h>  
  
// Function declarations  
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};  
void GetStringX(void);  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  
  
inline char* mygets(char* strDest, int n) {     
   char strExBuff[10];  
   char* pstrRet = fgets(strDest, n, stdin);  
  
   if (pstrRet == NULL)  
      return NULL;  
  
   // Exhaust the input buffer.  
   if (!strrchr(strDest, '\n'))  
      do {  
         fgets(strExBuff, sizeof(strExBuff), stdin);  
      } while (!strrchr(strExBuff, '\n'));  
   else  
      // Replace '\n' with '\0'  
      strDest[strrchr(strDest, '\n') - strDest] = '\0';  
  
   return pstrRet;  
}  
  
int main() {  
   if (FAILED(::CoInitialize(NULL)))  
      return -1;  
   GetStringX();  
   ::CoUninitialize();  
}  
  
void GetStringX() {  
   HRESULT  hr = S_OK;  
  char * token1;  
  
   // Define ADO object pointers.  
   // Initialize pointers on define.  
   // These are in the ADODB::  namespace.  
   _ConnectionPtr pConnection = NULL;  
   _RecordsetPtr pRstAuthors = NULL;  
  
   // Define string variables.  
   _bstr_t strCnn("Provider='sqloledb'; Data Source=My_Data_Source; Initial Catalog='pubs'; Integrated Security='SSPI';");  
   _bstr_t varOutput;   
   char *strPrompt = "Enter a state (CA, IN, KS, MD, MI, OR, TN, UT): ";  
   char strState[3], *pState;  
  
   try {  
      // Open connection.  
      TESTHR(pConnection.CreateInstance(__uuidof(Connection)));  
  
      // Open a command object for a stored procedure,   
      // with one parameter.  
      TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));  
  
      printf("%s",strPrompt);  
      mygets(strState, 3);  
  
      pState = strtok_s(strState," \t", &token1);  
  
      char strQry[100];  
      _snprintf_s(strQry, _countof(strQry), sizeof(strQry)-1, "SELECT au_fname, au_lname, address, city "  
         "FROM authors WHERE state = '%s'", pState);  
      strQry[sizeof(strQry)-1] = '\0';  
  
      pConnection->Open (strCnn, "", "", adConnectUnspecified);  
  
      pRstAuthors->Open(strQry, _variant_t((IDispatch*)pConnection, true),   
         adOpenStatic, adLockReadOnly, adCmdText);  
  
      if (pRstAuthors->RecordCount > 0)  {  
         // Use all defaults: get all rows, TAB column delimiter,   
         // CARRIAGE RETURN row delimiter, empty-string null delimiter  
         long lRecCount =  pRstAuthors->RecordCount;  
         _bstr_t varTab("\t");  
         _bstr_t varRet("\r");  
         _bstr_t varNull("");  
         varOutput = pRstAuthors->GetString(adClipString, lRecCount, varTab, varRet, varNull);  
         printf("State = '%s'\n", strState);  
         printf ("Name            Address            City\n");  
         printf ("%s\n", (LPCTSTR)varOutput);  
      }  
      else  
         printf("\nNo rows found for state = '%s'\n", pState);  
   }   
   catch(_com_error &e) {  
      // Notify the user of errors if any.  
      // Pass a connection pointer accessed from the Recordset.  
      PrintProviderError(pConnection);  
      PrintComError(e);  
   }  
  
   // Clean up objects before exit.  
   if (pRstAuthors)  
      if (pRstAuthors->State == adStateOpen)  
         pRstAuthors->Close();  
   if (pConnection)  
      if (pConnection->State == adStateOpen)  
         pConnection->Close();  
}  
  
void PrintProviderError(_ConnectionPtr pConnection) {  
   // Print Provider Errors from Connection object.  
   // pErr is a record object in the Connection's Error collection.  
   ErrorPtr pErr = NULL;  
  
   if( (pConnection->Errors->Count) > 0) {  
      long nCount = pConnection->Errors->Count;  
      // Collection ranges from 0 to nCount -1.  
      for (long i = 0 ; i < nCount ; i++) {  
         pErr = pConnection->Errors->GetItem(i);  
         printf("\t Error number: %x\t%s", pErr->Number, pErr->Description);  
      }  
   }  
}  
  
void PrintComError(_com_error &e) {  
   _bstr_t bstrSource(e.Source());  
   _bstr_t bstrDescription(e.Description());  
  
   // Print Com errors.  
   printf("Error\n");  
   printf("\tCode = %08lx\n", e.Error());  
   printf("\tCode meaning = %s\n", e.ErrorMessage());  
   printf("\tSource = %s\n", (LPCSTR) bstrSource);  
   printf("\tDescription = %s\n", (LPCSTR) bstrDescription);  
  
}  

示例输入

MD  

示例输出

Enter a state (CA, IN, KS, MD, MI, OR, TN, UT): State = 'md'  
Name            Address            City  
Sylvia   Panteley   1956 Arlington Pl.   Rockville  

另请参阅

GetString 方法 (ADO)
记录集对象 (ADO)