Type 屬性範例 (Field) (VC++)
這個範例示範 Type 屬性,方法是顯示常數的名稱,該常數對應至 Employees 資料表中所有 Field 物件的 Type 屬性值。 需要 FieldType 函式,此程序才能執行。
範例
// BeginTypeFieldCpp.cpp
// compile with: /EHsc
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")
#include <ole2.h>
#include <stdio.h>
#include <conio.h>
// Function declarations
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };
void TypeX();
_bstr_t FieldType(int intType);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
int main() {
if ( FAILED(::CoInitialize(NULL)) )
return -1;
TypeX();
::CoUninitialize();
}
void TypeX() {
// Define string variables.
_bstr_t strCnn("Provider='sqloledb'; Data Source='(local)'; Initial Catalog='pubs'; Integrated Security='SSPI';");
// Define ADO object pointers, initialize pointers. These are in the ADODB:: namespace.
_RecordsetPtr pRstEmployees = NULL;
FieldsPtr pFldLoop = NULL;
try {
// Open recordset with data from Employee table.
TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));
pRstEmployees->Open ("employee", strCnn, adOpenForwardOnly, adLockReadOnly, adCmdTable);
printf("Fields in Employee Table:\n\n");
// Enumerate the Fields collection of the Employees table.
pFldLoop = pRstEmployees->GetFields();
for (short int intFields = 0 ; intFields < (int)pFldLoop->GetCount() ; intFields++) {
_variant_t Index;
Index.vt = VT_I2;
Index.iVal = intFields;
printf(" Name: %s\n" , (LPCSTR) pFldLoop->GetItem(Index)->GetName());
printf(" Type: %s\n\n", (LPCTSTR)FieldType(pFldLoop->GetItem(Index)->Type));
}
}
catch (_com_error &e) {
// Display errors, if any. Pass connection pointer accessed from the Recordset.
_variant_t vtConnect = pRstEmployees->GetActiveConnection();
// GetActiveConnection returns connect string if connection
// is not open, else returns Connection object.
switch(vtConnect.vt) {
case VT_BSTR:
PrintComError(e);
break;
case VT_DISPATCH:
PrintProviderError(vtConnect);
break;
default:
printf("Errors occured.");
break;
}
}
// Clean up objects before exit.
if (pRstEmployees)
if (pRstEmployees->State == adStateOpen)
pRstEmployees->Close();
}
_bstr_t FieldType(int intType) {
_bstr_t strType;
switch(intType) {
case adChar:
strType = "adChar";
break;
case adVarChar:
strType = "adVarChar";
break;
case adSmallInt:
strType = "adSmallInt";
break;
case adUnsignedTinyInt:
strType = "adUnsignedTinyInt";
break;
case adDBTimeStamp:
strType = "adDBTimeStamp";
break;
default:
break;
}
return strType;
}
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("Error number: %x\t%s\n", pErr->Number, (LPCSTR) 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);
}
員工資料表中的欄位:
名稱:emp_id
類型:adChar
名稱:fname
類型:adVarChar
名稱:minit
類型:adChar
名稱:lname
類型:adVarChar
名稱:job_id
類型:adSmallInt
名稱:job_lvl
類型:adUnsignedTinyInt
名稱:pub_id
類型:adChar
名稱:hire_date
類型:adDBTimeStamp
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