为什么我不能在一个方法中两次调用OpenConnection()?当我调用它时会出现此错误:
连接已经打开。
我在SelectDisPatient()
和Count()
中称呼它两次。请参阅for (int index = 0; index < Count(); index++)
此方法SelectDisPatient
:
public void SelectDisPatient(FrmVIRGO frm)
{
string query = "SELECT id_pasien FROM tb_patient_information ";
if (this.OpenConnection() == true)
{ //Create Command
MySqlCommand cmd = new MySqlCommand(query, connection);
//Create a data reader and Execute the command
MySqlDataReader dataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
if (dataReader.HasRows)
{
for (int index = 0; index < Count(); index++)
dataReader.Read();
frm.tbName.Text = dataReader[0].ToString();
}
//close Data Reader
dataReader.Close();
//close Connection
this.CloseConnection();
}
}
这个Count()
方法:
public int Count()
{
string query = "SELECT Count(*) FROM tb_patient_information";
int Count = -1;
//Open Connection
if (this.OpenConnection() == true)
{
//Create Mysql Command
MySqlCommand cmd = new MySqlCommand(query, connection);
//ExecuteScalar will return one value
Count = int.Parse(cmd.ExecuteScalar()+"");
//close Connection
this.CloseConnection();
return Count;
}
else
{
return Count;
}
}
但是当我在(this.OpenConnection() == true)
方法中移除Count()
时,我说我需要关闭连接。
答案 0 :(得分:2)
尝试:
public void SelectDisPatient(FrmVIRGO frm)
{
int count = Count();
string query = "SELECT id_pasien FROM tb_patient_information ";
if (this.OpenConnection() == true)
{ //Create Command
MySqlCommand cmd = new MySqlCommand(query, connection);
//Create a data reader and Execute the command
MySqlDataReader dataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
if (dataReader.HasRows)
{
for (int index = 0; index < count ; index++)
dataReader.Read();
frm.tbName.Text = dataReader[0].ToString();
}
//close Data Reader
dataReader.Close();
//close Connection
this.CloseConnection();
}
}