Use the Visual FoxPro ODBC Driver with Your C or Visual C++ Application

Your C or C++ application communicates with Visual FoxPro data by sending a SQLExecute or SQLExecDirect statement to Visual FoxPro. This statement can contain the following:

Example: Using the Visual FoxPro ODBC Driver with Your C or C++ Application

The following example uses the ODBC C API to retrieve data stored in the last_name field in the employee table in the Microsoft® Visual FoxPro sample database named TasTrade. This database is provided with Visual FoxPro and is installed by default in the following location:

c:\vfp\samples\mainsamp\data\tastrade.dbc

The example displays one last name at a time, allowing you to click OK on the message box to see the next last name. It is assumed that a data source named Tastrade has been set up to use the Tastrade.dbc database.

Note

Error checking should be performed on all ODBC API calls; this example excludes error checking for the sake of brevity.

// FoxPro_ODBC_Driver_with_C.cpp  
// compile with: odbc32.lib user32.lib /c  
#include <windows.h>  
#include <sql.h>  
#include <sqlext.h>  
#include <stdio.h>  
#include <mbstring.h>  

#define MAX_DATA 100  
#define MYSQLSUCCESS(rc) ((rc==SQL_SUCCESS)||(rc==SQL_SUCCESS_WITH_INFO))  

class direxec {  
   RETCODE rc;        // ODBC return code  
   HENV henv;         // Environment     
   HDBC hdbc;         // Connection handle  
   HSTMT hstmt;       // Statement handle  
   unsigned char szData[MAX_DATA];   // Returned data storage  
   SDWORD cbData;     // Output length of data  
   unsigned char chr_ds_name[SQL_MAX_DSN_LENGTH];   // Data source name  

public:  
   direxec();           // Constructor  
   void sqlconn();      // Allocate env, stat, and conn  
   void sqlexec(unsigned char *);   // Execute SQL statement  
   void sqldisconn();   // Free pointers to env, stat, conn, and disconnect  
   void error_out();    // Displays errors  
};  

// Constructor initializes the string chr_ds_name with the data source name.  
direxec::direxec() {  
   _mbscpy_s(chr_ds_name, (const unsigned char *)"tastrade");  
}  

// Allocate environment handle, allocate connection handle,  
// connect to data source, and allocate statement handle.  
void direxec::sqlconn() {  
   SQLAllocEnv(&henv);  
   SQLAllocConnect(henv, &hdbc);  
   rc=SQLConnect(hdbc, chr_ds_name, SQL_NTS, NULL, 0, NULL, 0);  

   // Deallocate handles, display error message, and exit.  
   if (!MYSQLSUCCESS(rc)) {  
      SQLFreeEnv(henv);  
      SQLFreeConnect(hdbc);  
      error_out();  
      exit(-1);  
   }  

   rc = SQLAllocStmt(hdbc, &hstmt);  
}  

// Execute SQL command with SQLExecDirect() ODBC API.  
void direxec::sqlexec(unsigned char * cmdstr) {  
   rc = SQLExecDirect(hstmt, cmdstr, SQL_NTS);  
   if (!MYSQLSUCCESS(rc)) {   // Error  
      error_out();  
      // Deallocate handles and disconnect.  
      SQLFreeStmt(hstmt, SQL_DROP);  
      SQLDisconnect(hdbc);  
      SQLFreeConnect(hdbc);  
      SQLFreeEnv(henv);  
      exit(-1);  
   }  
   else {  
      for (rc = SQLFetch(hstmt) ; rc == SQL_SUCCESS; rc=SQLFetch(hstmt)) {  
         SQLGetData(hstmt, 1, SQL_C_CHAR, szData, sizeof(szData), &cbData);  
         // In this example, the data is returned in a messagebox for  
         // simplicity. However, normally the SQLBindCol() ODBC API could  
         // be called to bind individual data rows and assign for a rowset.  
         MessageBox(NULL, (const char *)szData, "ODBC", MB_OK);  
      }  
   }  
}  

// Free the statement handle, disconnect, free the connection handle, and  
// free the environment handle.  
void direxec::sqldisconn() {  
   SQLFreeStmt(hstmt, SQL_DROP);  
   SQLDisconnect(hdbc);  
   SQLFreeConnect(hdbc);  
   SQLFreeEnv(henv);  
}  

// Display error message in a message box that has an OK button.  
void direxec::error_out() {  
   unsigned char szSQLSTATE[10];  
   SDWORD nErr;  
   unsigned char msg[SQL_MAX_MESSAGE_LENGTH + 1];  
   SWORD cbmsg;  

   while(SQLError(0, 0, hstmt, szSQLSTATE, &nErr, msg, sizeof(msg), &cbmsg) == SQL_SUCCESS) {  
      sprintf_s((char *)szData, MAX_DATA, "Error:\nSQLSTATE=%s, Native error=%ld, msg='%s'",   
         szSQLSTATE, nErr, msg);  

      MessageBox(NULL, (const char *)szData, "ODBC Error", MB_OK);  
   }  
}  

int main (){  
   // Declare an instance of the direxec object.  
   direxec x;  

   // Allocate handles and connect.  
   x.sqlconn();  

   // Execute SQL command "SELECT last_name FROM employee".  
   x.sqlexec((UCHAR FAR *)"SELECT last_name FROM employee");  

   // Free handles, and disconnect.  
   x.sqldisconn();  

   // Return success code; example executed successfully.  
   return (TRUE);  
}