using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
namespace ConsoleApplication5
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                string strcon = @"server=localhost;database=Test;uid=sa;pwd=sa";
                SqlConnection sqlconn = new SqlConnection(strcon);
                SqlCommand sqlcomm = sqlconn.CreateCommand();
                string commStr = "select * from student";
                 = commStr;
                sqlconn.Open();
                SqlDataReader myDateReader = sqlcomm.ExecuteReader();
                myDateReader.Read();
                Console.WriteLine("asdfasd");
                Console.ReadLine();
                sqlconn.Close();
            }
            catch (Exception e)
            {
                // MessageBox.Show("连接错误" + e.ToString());
                Console.WriteLine(e.ToString());
            }
            finally
            {
                Console.ReadLine();
            }
        }
    }
}


运行结果
System.Data.SqlClient.SqlException (0x80131904): 用户 'sa' 登录失败。原因: 未与
信任 SQL Server 连接相关联。
   在 System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception
, Boolean breakConnection)
   在 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning()
   在 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cm
dHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, Tds
ParserStateObject stateObj)
   在 System.Data.SqlClient.(Boolean enlis
tOK)
   在 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo
serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeo
ut, SqlConnection owningObject)
   在 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo
serverInfo, String newPassword, Boolean redirectedUserInstance, SqlConnection ow
ningObject, SqlConnectionString connectionOptions, TimeoutTimer timeout)
   在 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnecti
on owningObject, TimeoutTimer timeout, SqlConnectionString connectionOptions, St
ring newPassword, Boolean redirectedUserInstance)
   在 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdent
ity identity, SqlConnectionString connectionOptions, Object providerInfo, String

 newPassword, SqlConnection owningObject, Boolean redirectedUserInstance)
   在 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOp
tions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection

 owningConnection)
   在 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConn
ection owningConnection, DbConnectionPool pool, DbConnectionOptions options)
   在 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owning
Object)
   在 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection o
wningObject)
   在 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection ownin
gObject)
   在 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection ow
ningConnection)
   在 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection ou
terConnection, DbConnectionFactory connectionFactory)
   在 System.Data.SqlClient.SqlConnection.Open()
   在 ConsoleApplication5.Program.Main(String[] args) 位置 D:\C#workspace\Consol
eApplication6\ConsoleApplication6\Program.cs:行号 19

老是连不上，但是绑定可以，大家帮忙看看

SqlServer中身份验证要设置为sql server和windows身份验证模式，然后要启用sa用户
具体步骤可百度一下

如果多次使用连接的话，那个SQL连接语句要写多少次啊！              

数据库连接字符串写在一个地方其他地方调用即可

----------------------------------------------连接数据库类----------------------------------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace WindowsFormsApplication5
{
    class DBHelper
    {
        const string CONNECTIONSTRING = "Data Source=.\\sql2008;Initial Catalog= MyQQ;Integrated Security=True";
        public static SqlConnection GetCon()
        {
            return new SqlConnection(CONNECTIONSTRING);
        }
    }
}
--------------------------------------------------------使用方法----------------------------------------------------------------
using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace WindowsFormsApplication5
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

  

        private void Form1_Load(object sender, EventArgs e)
        {
            LoadMima();
            NewMethod();
            SqlConnection conn = DBHelper.GetCon();
            string sql = "select bloodtype from bloodtype";
            SqlCommand command = new SqlCommand(sql,conn);
            conn.Open();
            SqlDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                cboBloodType.Items.Add(reader["bloodtype"].ToString());
            }
            reader.Close();
            conn.Close();
        }

WO 是问版主的    O(∩_∩)O哈哈~

    是提问者，不好意思啊,版主   
    不好意思啊,版主
不好意思啊,版主
不好意思啊,版主
不好意思啊,版主
不好意思啊,版主

    是提问者，不好意思啊,版主   
    不好意思啊,版主
    不好意思啊,版主
    不好意思啊,版主
    不好意思啊,版主
    不好意思啊,版主

这个问题我也有过你可以先用无密码登录，然后再左侧树节点根处点击右键找到属性-->安全性-->服务器身份验证-->SQL Server 和 Windows身份验证模式--> 最后重启服务.