C#用户设置界面(一):SQL如何查找利用返回值

Define.connectstring = "Data Source=105.147.202.11;Initial Catalog=clearer;User ID=**;Password=*************.";
Define.sqlConnection = new SqlConnection(Define.connectstring);

if (Define.sqlConnection.State.Equals(ConnectionState.Closed))//判断当前数据库状态，是否打开
Define.sqlConnection.Open();

SqlCommand SqlCom = new SqlCommand(); //新建了命令类
string execstring;
execstring = "select 用户密码 from table1 用户名='" + username + "'"; //SQL控制语句,username是外部变量

SqlCom.Connection = Define.sqlConnection; //连接地址
SqlCom.CommandText = execstring; //控制命令
SqlCom.ExecuteNonQuery(); //执行命令
SqlDataReader dataReader = SqlCom.ExecuteReader(); //定义读取流
if (dataReader.Read())
{
password = Convert.ToString(dataReader[0]); //读取返回数组第一列，即用户密码列第一个
dataReader.Close();
Define.sqlConnection.Close(); //关闭
return password; //返回获得的用户密码
}
else
{
dataReader.Close();
Define.sqlConnection.Close();
password = "查找无此用户";
return password;
}