连不上mysql数据库（未将对象引用到对象的实例）
public class User:
SRMS.IDataAccessLayer.IUser
{
#region IUser 成员
string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["conn"].ConnectionString;
private const string ValidateUserSQL
= "select UserId from users where UserName=@username and Password=@password";
//定义参数
private const string usernameParameter = "@username";
private const string passwordParameter = "@password";
public bool ValidateUser(string username, string password)
{
//定义参数对象
MySqlParameter pName = new MySqlParameter(usernameParameter, MySqlDbType.VarChar, 50);
MySqlParameter pPwd = new MySqlParameter(passwordParameter, MySqlDbType.VarChar, 50);
//为对象赋值
pName.Value = username;
pPwd.Value = password;
//执行sql语句
using (MySqlConnection connection = new MySqlConnection(connectionString))
{
MySqlCommand command = new MySqlCommand(ValidateUserSQL, connection);
connection.Open();
command.Parameters.Add("@username", MySqlDbType.VarChar).Value = username;
command.Parameters.Add("@password", MySqlDbType.VarChar).Value = password;
object result= command.ExecuteScalar();
//如果有查到，返回值就不为null
return result != null;
}
}
//////////////////////////////////////////我用的是MySql数据库
string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["conn"].ConnectionString; 错误提示：未将对象引用到对象的实例
配置文件时这样写的：
<connectionStrings>
<add name="conn" connectionString="host=127.0.0.1;database=mysrms;uid=root;pwd=123;"/>
</connectionStrings>
[解决办法]
你数据库连接字符串写的有问题
这样写
<connectionStrings>
<add name="conn"
connectionString="server=localhost;User Id=root;password=123;Persist Security Info=True;database=mysrms"
providerName="MySql.Data.MySqlClient" />
</connectionStrings>
