Fill: SelectCommand.Connection 属性尚未初始化。

Question

随便写写。练习的。自己写的类。
老是出现Fill: SelectCommand.Connection 属性尚未初始化。using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;namespace DAL
{
    public class DBhelpe
    {
        private static SqlConnection conn;
        public static SqlConnection Conn
        {
            get
            {
                string connectionString = ConfigurationManager.ConnectionStrings["HB"].ConnectionString;
                if (conn == null) 
                 {
                     conn = new SqlConnection(connectionString);
                     conn.Open();
                 }
                 else if (conn.State == System.Data.ConnectionState.Closed) 
                 {
                     conn.Open();
                 }else if(conn.State==System.Data.ConnectionState.Broken)
                 {
                     conn.Close();
                     conn.Open();
                 }
                 return conn;
            }
        }
        public static int ExecuteCommand(string sql) 
        {
            SqlCommand com = new SqlCommand(sql,conn);
            int num = com.ExecuteNonQuery();
            return num;
        }
        public static int ExecuteCommand(string sql, SqlParameter[] values) 
        {
            SqlCommand com = new SqlCommand(sql, conn);
            com.Parameters.AddRange(values);
            int num = com.ExecuteNonQuery();
            return num;
        }
        public static SqlDataReader reder(string sql) 
        {
            SqlCommand com = new SqlCommand(sql, conn);
            SqlDataReader reder = com.ExecuteReader();
            return reder;
        }
        public static SqlDataReader reder(string sql, SqlParameter[] values) 
        {
            SqlCommand com = new SqlCommand(sql, conn);
            com.Parameters.AddRange(values);
            SqlDataReader reder = com.ExecuteReader();
            return reder;
        }
        public static DataTable dataTable(string sql) 
        {
            DataSet ds = new DataSet();
            SqlCommand com = new SqlCommand(sql, conn);
            SqlDataAdapter da = new SqlDataAdapter(com);
            da.Fill(ds);
            return ds.Tables[0];
        }
        public static DataTable dataTable(string sql, SqlParameter[] values) 
        {
            DataSet ds = new DataSet();
            SqlCommand com = new SqlCommand(sql, conn);
            com.Parameters.AddRange(values);
            SqlDataAdapter da = new SqlDataAdapter(com);
            da.Fill(ds);
            return ds.Tables[0];
        }
    }
}

Answer 1

把SqlCommand com = new SqlCommand(sql,conn);
这种改成SqlCommand com = new SqlCommand(sql,Conn);你的Connection对象是在属性里初始化的。
另外最好不要用静态的Connection，并发时会有问题。