using
在using代码块内所有可能的位置创建短期生存对象
使用NextResult()取多个结果集
参数化查询
设置一个NULL 值 使用 DBNull.Value
返回 ojbect[]
new object[] {...}
DataTable[] tables = new DataTable() {ds.Table[1],ds.Table[1]}
添加行 LoadDataRow
在using代码块内所有可能的位置创建短期生存对象
使用NextResult()取多个结果集
SqlConnection con = new SqlConnection("data source=(local);initial catalog=ThreeLayer;persist security info=False;user id=sa;password=;");
con.Open();
SqlCommand cmd = con.CreateCommand();
cmd.CommandText = "select * from Limit; select * from Message";
SqlDataReader dr = cmd.ExecuteReader();
//使用NextResult()取多个结果集
//do
//{
// while (dr.Read())
// {
// Console.Write("{0}-{1}",dr[0],dr[1]);
// Console.WriteLine();
// }
//} while (dr.NextResult());
//Read())方法 取一个
while (dr.Read())
{
Console.Write("{0}-{1}", dr[0], dr[1]);
Console.WriteLine();
}
dr.Close();
con.Close();
con.Open();
SqlCommand cmd = con.CreateCommand();
cmd.CommandText = "select * from Limit; select * from Message";
SqlDataReader dr = cmd.ExecuteReader();
//使用NextResult()取多个结果集
//do
//{
// while (dr.Read())
// {
// Console.Write("{0}-{1}",dr[0],dr[1]);
// Console.WriteLine();
// }
//} while (dr.NextResult());
//Read())方法 取一个
while (dr.Read())
{
Console.Write("{0}-{1}", dr[0], dr[1]);
Console.WriteLine();
}
dr.Close();
con.Close();
参数化查询
string strConn, strSQL;
strConn = @"Data Source=.\SQLExpress;" +
"Initial Catalog=Northwind;Integrated Security=True;";
strSQL = "SELECT @UnitPrice = UnitPrice, @UnitsInStock = UnitsInStock " +
"FROM Products WHERE ProductName = @ProductName";
SqlConnection cn = new SqlConnection(strConn);
cn.Open();
SqlCommand cmd = new SqlCommand(strSQL, cn);
SqlParameter pUnitPrice, pInStock, pProductName;
pUnitPrice = cmd.Parameters.Add("@UnitPrice", SqlDbType.Money);
pUnitPrice.Direction = ParameterDirection.Output;
pInStock = cmd.Parameters.Add("@UnitsInStock", SqlDbType.NVarChar, 20);
pInStock.Direction = ParameterDirection.Output;
pProductName = cmd.Parameters.Add("@ProductName", SqlDbType.NVarChar, 40);
pProductName.Value = "Chai";
cmd.ExecuteNonQuery();
if (pUnitPrice.Value == DBNull.Value) {
Console.WriteLine("No product found named {0}", pProductName.Value);
} else {
Console.WriteLine("Unit Price: {0}", pUnitPrice.Value);
Console.WriteLine("In Stock: {0}", pInStock.Value);
}
strConn = @"Data Source=.\SQLExpress;" +
"Initial Catalog=Northwind;Integrated Security=True;";
strSQL = "SELECT @UnitPrice = UnitPrice, @UnitsInStock = UnitsInStock " +
"FROM Products WHERE ProductName = @ProductName";
SqlConnection cn = new SqlConnection(strConn);
cn.Open();
SqlCommand cmd = new SqlCommand(strSQL, cn);
SqlParameter pUnitPrice, pInStock, pProductName;
pUnitPrice = cmd.Parameters.Add("@UnitPrice", SqlDbType.Money);
pUnitPrice.Direction = ParameterDirection.Output;
pInStock = cmd.Parameters.Add("@UnitsInStock", SqlDbType.NVarChar, 20);
pInStock.Direction = ParameterDirection.Output;
pProductName = cmd.Parameters.Add("@ProductName", SqlDbType.NVarChar, 40);
pProductName.Value = "Chai";
cmd.ExecuteNonQuery();
if (pUnitPrice.Value == DBNull.Value) {
Console.WriteLine("No product found named {0}", pProductName.Value);
} else {
Console.WriteLine("Unit Price: {0}", pUnitPrice.Value);
Console.WriteLine("In Stock: {0}", pInStock.Value);
}
设置一个NULL 值 使用 DBNull.Value
返回 ojbect[]
new object[] {...}
DataTable[] tables = new DataTable() {ds.Table[1],ds.Table[1]}
添加行 LoadDataRow