在C#中为一组记录连接和查询数据库的最简单方法是什么?
答案 0 :(得分:30)
@Goyuix - 这对于从记忆中写的东西来说非常好。 在这里测试它 - 发现连接没有打开。否则非常好。
using System.Data.OleDb;
...
using (OleDbConnection conn = new OleDbConnection())
{
conn.ConnectionString = "Provider=sqloledb;Data Source=yourServername\\yourInstance;Initial Catalog=databaseName;Integrated Security=SSPI;";
using (OleDbCommand cmd = new OleDbCommand())
{
conn.Open();
cmd.Connection = conn;
cmd.CommandText = "Select * from yourTable";
using (OleDbDataReader dr = cmd.ExecuteReader())
{
while (dr.Read())
{
Console.WriteLine(dr["columnName"]);
}
}
}
}
答案 1 :(得分:16)
由于我的笔记本电脑上没有代码,因此非常粗略地从内存中获取:
using (OleDBConnection conn = new OleDbConnection())
{
conn.ConnectionString = "Whatever connection string";
using (OleDbCommand cmd = new OleDbCommand())
{
cmd.Connection = conn;
cmd.CommandText = "Select * from CoolTable";
using (OleDbDataReader dr = cmd.ExecuteReader())
{
while (dr.Read())
{
// do something like Console.WriteLine(dr["column name"] as String);
}
}
}
}
答案 2 :(得分:11)
这绝对是一个很好的方法。但是,如果您碰巧使用支持LINQ to SQL的数据库,那么它可能会更有趣。它看起来像这样:
MyDB db = new MyDB("Data Source=...");
var q = from db.MyTable
select c;
foreach (var c in q)
Console.WriteLine(c.MyField.ToString());
答案 3 :(得分:7)
这是另一种方式(DataReader比这个更快):
string s = "";
SqlConnection conn = new SqlConnection("Server=192.168.1.1;Database=master;Connect Timeout=30;User ID=foobar;Password=raboof;");
SqlDataAdapter da = new SqlDataAdapter("SELECT TOP 5 name, dbid FROM sysdatabases", conn);
DataTable dt = new DataTable();
da.Fill(dt);
for (int i = 0; i < dt.Rows.Count; i++)
{
s += dt.Rows[i]["name"].ToString() + " -- " + dt.Rows[i]["dbid"].ToString() + "\n";
}
MessageBox.Show(s);
答案 4 :(得分:4)
如果您打算阅读大量的列或记录,还值得缓存序数并访问强类型方法,例如
using (DbDataReader dr = cmd.ExecuteReader()) {
if (dr.Read()) {
int idxColumnName = dr.GetOrdinal("columnName");
int idxSomethingElse = dr.GetOrdinal("somethingElse");
do {
Console.WriteLine(dr.GetString(idxColumnName));
Console.WriteLine(dr.GetInt32(idxSomethingElse));
} while (dr.Read());
}
}
答案 5 :(得分:3)
如果要查询SQL Server数据库(版本7及更高版本),则应将OleDb类替换为System.Data.SqlClient命名空间中的相应类(SqlConnection,SqlCommand和{{3这些类已经过优化,可以与SQL Server一起使用。
另外需要注意的是,您应该“永远”选择全部,因为如果您向此表添加或删除列,这可能会导致以后出现意外结果。
答案 6 :(得分:1)
我想,你可以尝试实体框架。
using (SchoolDBEntities ctx = new SchoolDBEntities())
{
IList<Course> courseList = ctx.GetCoursesByStudentId(1).ToList<Course>();
//do something with courselist here
}
答案 7 :(得分:0)
为库收费
using MySql.Data.MySqlClient;
这是连接:
public static MySqlConnection obtenerconexion()
{
string server = "Server";
string database = "Name_Database";
string Uid = "User";
string pwd = "Password";
MySqlConnection conect = new MySqlConnection("server = " + server + ";" + "database =" + database + ";" + "Uid =" + Uid + ";" + "pwd=" + pwd + ";");
try
{
conect.Open();
return conect;
}
catch (Exception)
{
MessageBox.Show("Error. Ask the administrator", "An error has occurred while trying to connect to the system", MessageBoxButtons.OK, MessageBoxIcon.Error);
return conect;
}
}