类型的未处理的异常'System.InvalidOperationException'出现在system.data.dll当我试图将数据插入文本框

问题描述

我创建从Visual Studio中我的数据库的连接。

i am creating a connection to my database from from visual studio.

这是我的code：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;


public partial class CM : System.Web.UI.Page
{
    SqlConnection con = new SqlConnection("server =KIRITI; database =msdb; Integrated Security=True");

protected void Button1_Click(object sender, EventArgs e)
{
    con.Open();
    String NotesMaker = TextBox1.Text;
    SqlCommand cmd = new SqlCommand("Insert into NOTESMAKER(NOTESMAKER) Values('"+NotesMaker+"',con)");
    cmd.ExecuteNonQuery();
    cmd.CommandText = "Select@@Identity";
    con.Close();
}
}

我得到command.Executenonquery（）的错误：类型的异常'System.InvalidOperationException'出现在system.data.dll但在用户code没有处理

I get an error at command.Executenonquery(): An exception of type 'System.InvalidOperationException' occurred in System.Data.dll but was not handled in user code

更多信息：的ExecuteNonQuery：Connection属性尚未初始化

Additional information: ExecuteNonQuery: Connection property has not been initialized.

请帮助！我从两天受阻！

Please help!! I'm blocked from two days!!

推荐答案

的这就是连接首先，我所看到的字符串连接导致要查询的一部分的

Thats the first place where I have seen string concatenation causing conn to be part of query.

您错位字符串引号，你的说法应该是：

You misplaced string quotes, your statement should be:

SqlCommand cmd =
  new SqlCommand("Insert into NOTESMAKER(NOTESMAKER) Values('" + NotesMaker + "'",con);

在你目前的code，你通过字符串INSERT INTO NOTESMAKER（NOTESMAKER）VALUES（'+ NotesMaker +'，CON），因此，连接属性没有初始化，因此例外。

In your current code, you are passing string "Insert into NOTESMAKER(NOTESMAKER) Values('"+NotesMaker+"',con)", hence the connection property is not initialized and hence the exception.

您不应该使用字符串连接创建查询，而是使用参数。这将节省您从。这样的：

You should never use string concatenation for creating queries, instead use Parameters. This will save you from SQL Injection. Like:

using(SqlConnection con = new SqlConnection("connectionstring"))
using(SqlCommand cmd = new SqlCommand("Insert into NOTESMAKER(NOTESMAKER) Values(@NotesMaker)",con))
{
    cmd.Parameters.AddWithValue("@NotesMaker", NotesMaker);
    con.Open();
    cmd.ExecuteNonQuery();
}

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