操作数据库的SqlHelper类

public static class SqlHelper
{
public static readonly string connstr =
ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;

public static SqlConnection OpenConnection()
{
SqlConnection conn = new SqlConnection(connstr);
conn.Open();
return conn;
}

public static int ExecuteNonQuery(string cmdText,
params SqlParameter[] parameters)
{
using (SqlConnection conn = new SqlConnection(connstr))
{
conn.Open();
return ExecuteNonQuery(conn, cmdText, parameters);
}
}

public static object ExecuteScalar(string cmdText,
params SqlParameter[] parameters)
{
using (SqlConnection conn = new SqlConnection(connstr))
{
conn.Open();
return ExecuteScalar(conn, cmdText, parameters);
}
}

public static DataTable ExecuteDataTable(string cmdText,
params SqlParameter[] parameters)
{
using (SqlConnection conn = new SqlConnection(connstr))
{
conn.Open();
return ExecuteDataTable(conn, cmdText, parameters);
}
}

public static int ExecuteNonQuery(SqlConnection conn,string cmdText,
params SqlParameter[] parameters)
{
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
return cmd.ExecuteNonQuery();
}
}

public static object ExecuteScalar(SqlConnection conn, string cmdText,
params SqlParameter[] parameters)
{
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
return cmd.ExecuteScalar();
}
}

public static DataTable ExecuteDataTable(SqlConnection conn, string cmdText,
params SqlParameter[] parameters)
{
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
{
DataTable dt = new DataTable();
adapter.Fill(dt);
return dt;
}
}
}

public static object ToDBValue(this object value)
{
return value == null ? DBNull.Value : value;
}

public static object FromDBValue(this object dbValue)
{
return dbValue == DBNull.Value ? null : dbValue;
}
}