VC下的ADO编程入门(2-4)
好了，现在我们正式进入本主题，Let's go
n 新建一个基于对话的应用程序zjy，在对话框上添加一个按钮和列表控件，并把列表控件的样式设置为报表视图，还有用classwizard给列表控件添加一个控件变量m_list
n 在StdAfx.h头文件中添加一条如下语句
#import "c:\program files\common files\system\ado\msado15.dll" no_namespace rename("EOF","adoEOF")
n 在zjy.cpp开始处添加自动初始化COM库的代码
struct InitOle
{
InitOle(){::CoInitialize(NULL);}
~InitOle(){::CoUninitialize();}
}_init_InitOle_;
n 在zjyDlg.h中添加三个成员变量
bool m_IsConnectionOpen;
_ConnectionPtr m_pConnection;
_RecordsetPtr m_pRecordset;
n 在zjyDlg.cpp的BOOL CZjyDlg::OnInitDialog()的 return TRUE;前面添加如下代码
// TODO: Add extra initialization here
HRESULT hr;
_bstr_t bstrQuery("select * from customers");
_bstr_t strConnect="Provider=SQLOLEDB; data source=127.0.0.1;initial catalog=Northwind;";
_variant_t vRecsAffected(0L);
_variant_t vNULL;
vNULL.vt=VT_ERROR;
vNULL.scode =DISP_E_PARAMNOTFOUND;
try
{
hr=m_pConnection.CreateInstance(__uuidof(Connection));
if(SUCCEEDED(hr))
{
hr=m_pConnection->Open(strConnect,_bstr_t(L"sa"),_bstr_t(L""),adConnectUnspecified);
if(SUCCEEDED(hr))
{
hr=m_pRecordset.CreateInstance(__uuidof(Recordset));
if(SUCCEEDED(hr))
{
m_pRecordset->PutRefActiveConnection(m_pConnection);
hr=m_pRecordset->Open(_variant_t(bstrQuery),vNULL,adOpenDynamic,adLockOptimistic,adCmdText);
if(SUCCEEDED(hr))
{
m_IsConnectionOpen=true;
}
}
}
}
}
catch(_com_error &e)
{
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
TRACE("Exception throw for classes generated by #import");
TRACE("\tCode=%08lx\n", e.Error);
TRACE("\tCode meaning = %s\n", e.ErrorMessage);
TRACE("\tSource = %s\n", (LPCTSTR)bstrSource);
TRACE("\tDescription = %s\n", (LPCTSTR)bstrDescription);
}
catch(...)
{
TRACE("Unhandled Exception");
}
n 添加对话框的WM_Destroy消息响应函数
void CZjyDlg::OnDestroy()
{
CDialog::OnDestroy();
// TODO: Add your message handler code here
if(m_IsConnectionOpen)
{
m_IsConnectionOpen=false;
m_pConnection->Close();
m_pConnection=NULL;
m_pRecordset=NULL;
}
}
n 最后添加按钮的消息响应函数如下
void CZjyDlg::OnButton1()
{
// TODO: Add your control notification handler code here
VARIANT_BOOL valEof;
HRESULT hr;
CString strColName;BSTR bstrColName;
CString strValue;VARIANT varValue;
long ColCount,i; int RowCount=0;
Fields * fields=NULL;Field * field=NULL;
VARIANT varCounter;
varCounter.vt=VT_I4;
varCounter.lVal=0;
try
{
m_list.DeleteAllItems();
while(m_list.DeleteColumn(0));
hr=m_pRecordset->get_Fields(&fields);
if(SUCCEEDED(hr)) hr=fields->get_Count(&ColCount);
for(i=0;i<ColCount;i++)
{
hr=fields->Item[i]->get_Name(&bstrColName);
strColName=bstrColName;
int nWidth=m_list.GetStringWidth(strColName)+15;
m_list.InsertColumn(i,strColName,LVCFMT_LEFT,nWidth);
}
if(SUCCEEDED(hr)) fields->Release();
m_pRecordset->get_adoEOF(&valEof);
while(true)
{
if(valEof)break;
m_pRecordset->Fields->get_Item(varCounter,&field);
field->get_Value(&varValue);
strValue=VariantToString(varValue);
m_list.InsertItem(RowCount,strValue);
for(i=1;i<ColCount;i++)
{
varCounter.lVal =i;
m_pRecordset->Fields->get_Item(varCounter,&field);
field->get_Value(&varValue);
strValue=VariantToString(varValue);
m_list.SetItemText(RowCount,i,(LPCTSTR)strValue);
}
RowCount++;
m_pRecordset->MoveNext();
m_pRecordset->get_adoEOF(&valEof);
varCounter.lVal=0;
}
m_pRecordset->Close();
}
catch(_com_error &e)
{
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
TRACE("\tCode=%08lx\n", e.Error);
TRACE("\tCode meaning = %s\n", e.ErrorMessage);
TRACE("\tSource = %s\n", (LPCTSTR)bstrSource);
TRACE("\tDescription = %s\n", (LPCTSTR)bstrDescription);
}
catch(...)
{
}
}
n 还有还有，在对话框类添加一个数据类型转换函数
CString CZjyDlg::VariantToString(VARIANT var)
{
CString strValue;
_variant_t var_t;
_bstr_t bstr_t;
time_t cur_time;
CTime time_value;
COleCurrency var_currency;
switch(var.vt)
{
case VT_EMPTY:
case VT_NULL:strValue=_T("");break;
case VT_UI1:strValue.Format("%d",var.bVal);break;
case VT_I2:strValue.Format("%d",var.iVal);break;
case VT_I4:strValue.Format("%d",var.lVal);break;
case VT_R4:strValue.Format("%f",var.fltVal);break;
case VT_R8:strValue.Format("%f",var.dblVal);break;
case VT_CY:
var_currency=var;
strValue=var_currency.Format(0);break;
case VT_BSTR:
var_t =var;
bstr_t=var_t;
strValue.Format("%s",(const char *)bstr_t);break;
case VT_DATE:
cur_time=var.date;
time_value=cur_time;
strValue.Format("%A,%B,%d,%Y");break;
case VT_BOOL:strValue.Format("%d",var.boolVal);break;
default:strValue=_T("");break;
}
return strValue;
}
(完)
下一篇介绍如何对记录进行增删改操作。