ExecuteReader:连接属性没有初始化.如何解决这个问题

本文关键字：解决 问题 何解决 连接 属性 初始化 ExecuteReader | 更新日期: 2023-09-27 17:54:25

int tempid,temp1,temp2,temp3,temp4,temp5,temp6;
{
    SqlCommand cmd = new SqlCommand("select * from Szelvenyek");
    SqlConnection cn = new SqlConnection(@"Data Source=.'SQLEXPRESS;AttachDbFilename=D:'Iskola'C#'lotto_kerekeshunor'lotto_kerekeshunor'Database1.mdf;Integrated Security=True;User Instance=True");
    cn.Open();
    SqlDataReader dr = cmd.ExecuteReader();
    while (dr.Read())
    {
        tempid = (int)dr["ID"];
        temp1 = (int)dr["elso"];
        temp2 = (int)dr["masodik"];
        temp3 = (int)dr["harmadik"];
        temp4 = (int)dr["negyedik"];
        temp5 = (int)dr["otodik"];
        temp6 = (int)dr["hatodik"];
        if (r1 == temp1 || r1 == temp2 || r1 == temp3 || r1 == temp4 || r1 == temp5 || r1 == temp6) talalat[tempid]++;
        if (r2 == temp1 || r2 == temp2 || r2 == temp3 || r2 == temp4 || r2 == temp5 || r2 == temp6) talalat[tempid]++;
        if (r3 == temp1 || r3 == temp2 || r3 == temp3 || r3 == temp4 || r3 == temp5 || r3 == temp6) talalat[tempid]++;
        if (r4 == temp1 || r4 == temp2 || r4 == temp3 || r4 == temp4 || r4 == temp5 || r4 == temp6) talalat[tempid]++;
        if (r5 == temp1 || r5 == temp2 || r5 == temp3 || r5 == temp4 || r5 == temp5 || r5 == temp6) talalat[tempid]++;
        if (r6 == temp1 || r6 == temp2 || r6 == temp3 || r6 == temp4 || r6 == temp5 || r6 == temp6) talalat[tempid]++;
    }
}

我有这个代码，我想从数据库中读取数据，然后比较它们。Visual Basic显示

"ExecuteReader:连接属性尚未初始化。"

帮忙吗?

ExecuteReader:连接属性没有初始化.如何解决这个问题

看起来您没有初始化您的SqlCommand.Connection属性。如果没有这个，你的程序就不能知道用哪个SqlConnection来执行你的SqlCommand。只是添加;

cmd.Connection = cn;
cn.Open();
...

或者您可以将SqlConnection传递给SqlCommand构造函数作为第二个参数(我总是更喜欢)，如;

SqlCommand cmd = new SqlCommand("select * from Szelvenyek", cn);

还使用using语句来处理SqlConnection, SqlCommand和SqlDataReader;

using(SqlConnection cn = new SqlConnection(@"Data Source=.'SQLEXPRESS;AttachDbFilename=D:'Iskola'C#'lotto_kerekeshunor'lotto_kerekeshunor'Database1.mdf;Integrated Security=True;User Instance=True"))
using(SqlCommand cmd = new SqlCommand("select * from Szelvenyek", cn))
{
   cn.Open();
   using(SqlDataReader dr = cmd.ExecuteReader())
   {
      while(dr.Read())
      {
         ///
      }
   }
}

很容易忘记这一点。您可以手动设置该属性，也可以习惯在连接的之后构造命令，这样就可以将其传递给构造函数:

SqlConnection cn = new SqlConnection(@"Data Source=.'SQLEXPRESS;AttachDbFilename=D:'Iskola'C#'lotto_kerekeshunor'lotto_kerekeshunor'Database1.mdf;Integrated Security=True;User Instance=True");
SqlCommand cmd = new SqlCommand("select * from Szelvenyek", cn);
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