Question

以下查询未在数据库中插入值。

代码：

 try
 {
      for (int i = 0; i < listViewSubject.Items.Count; i+=2)
      {
           string query = "INSERT INTO Std_Subjects (subject_id, std_reg_id) VALUES ('" + listViewSubject.Items[i] + "', '" + this.reg_id + "')";
           dal.InsertUpdateDelete(query);
      }
      conn.Close();
 }
 catch (Exception ex)
 {
       MessageBox.Show(ex.ToString());
 }

Answer 1

根据您的问题，我理解转换为int时出现问题是错误的。您必须在插入前将主题ID转换为int。

    Try
        {
        for (int i = 0; i < listViewSubject.Items.Count; i+=2)
        {
            string query = "INSERT INTO Std_Subjects (subject_id, std_reg_id) VALUES (" + Int.Parse(listViewSubject.Items[i].Text) + ", " + this.reg_id + ")";
            dal.InsertUpdateDelete(query);
        }
        conn.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.ToString());
    }

希望this.reg_id也是int。如果没有转换它，因为我转换了主题ID。请注意，我已从

中删除了单引号

＆＃39;＆＃34; + listViewSubject.Items [i] +＆＃34;＆＃39;，＆＃39;＆＃34; + this.reg_id +＆＃34;＆＃39;

这是使用参数化查询的方法：

  for (int i = 0; i < listViewSubject.Items.Count; i+=2)
        {

         string query = "INSERT INTO Std_Subjects (subject_id, std_reg_id) VALUES (@subjectID,@StdRegId)";
         SqlCommand command = new SqlCommand(query, connection);
         command.Parameters.AddWithValue("@subjectID",Int.Parse(listViewSubject.Items[i].Text));
         command.Parameters.AddWithValue("@StdRegId", this.reg_id);
         command.ExecuteNonQuery();
        }

Answer 2

似乎listViewSubject.Items[i]返回一个值＆＃39; ListViewItem：{2}＆＃39}而不是整数。根据项集合返回的对象类型，您可能需要调试它。可能listViewSubject.Items[i].Value可能有用。

Answer 3

我不确定你的数据访问层究竟是在幕后做什么，但是使用基本的SqlCommand我倾向于按照以下方式进行插入：

string sql = "INSERT INTO Std_Subjects (subject_id, std_reg_id) VALUES (@SubjectID, @RegID)";
for (int i = 0; i < listViewSubject.Items.Count; i+=2)
{
    using (var conn = new SqlConnection(ConnectionString))
    using (var command = new SqlCommand(sql, connection))
    {
        conn.Open();
        command.Parameters.Add("@RegID", SqlDbType.Int).Value = this.reg_id;
        command.Parameters.Add(SubjectID, SqlDbType.Int).Value = listViewSubject[i].Text;
        command.ExecuteNonQuery();

    }
}

转换Varchar值时转换失败＆＃39; ListViewItem：{2}＆＃39;到数据类型int

3 个答案: