commandText属性尚未初始化

Question

窗体中有两个listview控件　当点击listview2中的某条记录时,listview１中就显示出相应的记录，可以，系统总提示我commandText属性尚未初始化，请问这是什么原因啊？！　代码如下：　请问代码有问题吗？！　谢谢！
private void Xflist()
        {
                       for (int i = 0; i < this.listView2.Items.Count; i++)
            {
                
                if (this.listView2.Items[i].Selected == true)
                {
                    
                    this.selectStr1 = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems[0].Text.ToString() + "'";
                    this.sqlCommand1.CommandText = this.selectStr1;                }
                
                    break;
            }                   
                    
                    try
                    {
                        this.sqlCommand1.CommandText = null;  
                        if (this.sqlConnection1.State == ConnectionState.Closed) this.sqlConnection1.Open(); //如果connection1关闭就打开
                       this.SqlDataReader1=this.sqlCommand1.ExecuteReader();  //用sqldatareadrer来读取数据库中的内容
                        while (this.SqlDataReader1.Read())
                        {
                            ListViewItem li = new ListViewItem();//生成新的listview的item
                            li.SubItems.Clear();//消除所有列的内容
                            li.SubItems[0].Text = SqlDataReader1["Ctid"].ToString();//给新记录第1列添加餐台号内容
                            li.SubItems.Add(SqlDataReader1["Xfitem"].ToString());
                            li.SubItems.Add(SqlDataReader1["Dj"].ToString());//给新记录第2列添加单价
                            li.SubItems.Add(SqlDataReader1["Dzbl"].ToString());//给新记录第3添加单价
                            li.SubItems.Add(SqlDataReader1["Sl"].ToString());//给新记录第4列添加数量
                            li.SubItems.Add(SqlDataReader1["Money"].ToString());
                            li.SubItems.Add(SqlDataReader1["FUs"].ToString());
                            li.SubItems.Add(SqlDataReader1["Bz"].ToString());
                            this.listView1.Items.Add(li);//把新记录添加到listview1中去                        }
                    }                    catch (System.Exception E)
                    {
                        MessageBox.Show(E.ToString());
                    }
                    finally
                    {                        this.sqlConnection1.Close();
                    }

Answer 1

方法体外有没有 SqlCommand sqlcommand1 = new SqlCommand()?

Answer 2

断点一下，看看this.selectStr1 = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems[0].Text.ToString() + "'";是什么

Answer 3

看看selectStr1的值是什么。 

Answer 4

看看selectStr1的值是什么。 

Answer 5

this.sqlCommand1.CommandText = null;  //???

Answer 6

你是不是这样做的 private SqlCommand sqlCommand1;
没有private SqlCommand sqlCommand1 = new SqlCommand();

Answer 7

 try 
                    { 
                        this.sqlCommand1.CommandText = null;  这是null了
                        if (this.sqlConnection1.State == ConnectionState.Closed) this.sqlConnection1.Open(); //如果connection1关闭就打开 
                      this.SqlDataReader1=this.sqlCommand1.ExecuteReader();  //用sqldatareadrer来读取数据库中的内容 
                        while (this.SqlDataReader1.Read()) 
                        { 
                            ListViewItem li = new ListViewItem();//生成新的listview的item 
                            li.SubItems.Clear();//消除所有列的内容 
                            li.SubItems[0].Text = SqlDataReader1["Ctid"].ToString();//给新记录第1列添加餐台号内容 
                            li.SubItems.Add(SqlDataReader1["Xfitem"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["Dj"].ToString());//给新记录第2列添加单价 
                            li.SubItems.Add(SqlDataReader1["Dzbl"].ToString());//给新记录第3添加单价 
                            li.SubItems.Add(SqlDataReader1["Sl"].ToString());//给新记录第4列添加数量 
                            li.SubItems.Add(SqlDataReader1["Money"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["FUs"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["Bz"].ToString()); 
                            this.listView1.Items.Add(li);//把新记录添加到listview1中去                         } 
                    } 

Answer 8

this.sqlCommand1.CommandText = null; 
这句去掉

Answer 9

就是这个原因，在try里面又清空了。

Answer 10

我把那行去掉了还是不行，显示     commandText属性尚未初始化  ，到底是哪里出问题了呢！？

Answer 11

sqlCommand1怎么来的？把这段代码发出来看一下。sqlCommand1=sqlConnection1.CreateCommand();
上面有这样一段代码吗？

Answer 12

把break写到if条件成立的语句块中去            for (int i = 0; i < this.listView2.Items.Count; i++) 
            { 
                
                if (this.listView2.Items[i].Selected == true) 
                { 
                    
                    this.selectStr1 = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems[0].Text.ToString() + "'"; 
                    this.sqlCommand1.CommandText = this.selectStr1;                     break;                 } 
                
            } 

Answer 13

try 
                    { 
                        this.sqlCommand1.CommandText = null;  这是null了 
                        if (this.sqlConnection1.State == ConnectionState.Closed) this.sqlConnection1.Open(); //如果connection1关闭就打开 
                      this.SqlDataReader1=this.sqlCommand1.ExecuteReader();  //用sqldatareadrer来读取数据库中的内容 
                        while (this.SqlDataReader1.Read()) 
                        { 
                            ListViewItem li = new ListViewItem();//生成新的listview的item 
                            li.SubItems.Clear();//消除所有列的内容 
                            li.SubItems[0].Text = SqlDataReader1["Ctid"].ToString();//给新记录第1列添加餐台号内容 
                            li.SubItems.Add(SqlDataReader1["Xfitem"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["Dj"].ToString());//给新记录第2列添加单价 
                            li.SubItems.Add(SqlDataReader1["Dzbl"].ToString());//给新记录第3添加单价 
                            li.SubItems.Add(SqlDataReader1["Sl"].ToString());//给新记录第4列添加数量 
                            li.SubItems.Add(SqlDataReader1["Money"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["FUs"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["Bz"].ToString()); 
                            this.listView1.Items.Add(li);//把新记录添加到listview1中去                         } 
                    } this.sqlCommand1.CommandText = null;之后就没有给this.sqlCommand1.CommandText赋值

Answer 14

15楼是对的。。break在if语句外面，循环只跑了一次，this.sqlCommand1.CommandText可能还没赋上值。。
另外，this.sqlCommand1.CommandText = null;肯定要去掉。

Answer 15

从你这段代码来看可能会有两个问题：for (int i = 0; i < this.listView2.Items.Count; i++)
{
if (this.listView2.Items[i].Selected == true)
{
   
    this.selectStr1 = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems[0].Text.ToString() + "'";
    this.sqlCommand1.CommandText = this.selectStr1;
            //break;似乎应该放在这里
}
break;       //这里循环跳出？似乎应该是放到if的括号里。
}  
   
try
{
this.sqlCommand1.CommandText = null;          //这里又==null这是什么意思？  

Answer 16

完整的代码是这样的
namespace CanYinManager
{
    public partial class FormMain : Form
    {
        private string selectStr1;        private SqlConnection sqlConnection1 = null;
         private SqlCommand sqlCommand1 = null;
 public FormMain()
        {
            //在构造函数中为变量赋值            InitializeComponent();//系统初始函数
            this.sqlConnection1 = new SqlConnection(CanYinManager.DataLevel.Connection.ConnString);
            this.sqlCommand1 = new SqlCommand();
            this.sqlCommand1.Connection = this.sqlConnection1;
        private void FormMain_Load(object sender, EventArgs e)
        { 
           this.UpdateListView();//更新listview显示内容
           this.Xflist();
        }
                   private void Xflist()
        {
            
            for (int i = 0; i < this.listView2.Items.Count;i++)
            {
                
                if (this.listView2.Items[i].Selected == true)
                {
                    
                    this.selectStr1 = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems[0].Text.ToString() + "'";
                    this.sqlCommand1.CommandText = this.selectStr1;
                    break;
                }
                
                    
            }                   
                    
                    try
                    {
                        
                       
                        if (this.sqlConnection1.State == ConnectionState.Closed) this.sqlConnection1.Open(); //如果connection1关闭就打开
                       this.SqlDataReader1=this.sqlCommand1.ExecuteReader();  //用sqldatareadrer来读取数据库中的内容
                        while (this.SqlDataReader1.Read())
                        {
                            ListViewItem li = new ListViewItem();//生成新的listview的item
                            li.SubItems.Clear();//消除所有列的内容
                            li.SubItems[0].Text = SqlDataReader1["Ctid"].ToString();//给新记录第1列添加餐台号内容
                            li.SubItems.Add(SqlDataReader1["Xfitem"].ToString());
                            li.SubItems.Add(SqlDataReader1["Dj"].ToString());//给新记录第2列添加单价
                            li.SubItems.Add(SqlDataReader1["Dzbl"].ToString());//给新记录第3添加单价
                            li.SubItems.Add(SqlDataReader1["Sl"].ToString());//给新记录第4列添加数量
                            li.SubItems.Add(SqlDataReader1["Money"].ToString());
                            li.SubItems.Add(SqlDataReader1["FUs"].ToString());
                            li.SubItems.Add(SqlDataReader1["Bz"].ToString());
                            this.listView1.Items.Add(li);//把新记录添加到listview1中去                        }
                    }                    catch (System.Exception E)
                    {
                        MessageBox.Show(E.ToString());
                    }
                    finally
                    {                        this.sqlConnection1.Close();
                    }          
        }
           
           
  }    
}

Answer 17

这个是完整的，上面的那个少了一条语句，我加上了这条语句还是不行！
namespace CanYinManager
{
    public partial class FormMain : Form
    {
        private string selectStr1;        private SqlConnection sqlConnection1 = null;
         private SqlCommand sqlCommand1 = null;
       private SqlDataReader SqlDataReader1 = null;
 public FormMain()
        {
            //在构造函数中为变量赋值            InitializeComponent();//系统初始函数
            this.sqlConnection1 = new SqlConnection(CanYinManager.DataLevel.Connection.ConnString);
            this.sqlCommand1 = new SqlCommand();
            this.sqlCommand1.Connection = this.sqlConnection1;
        private void FormMain_Load(object sender, EventArgs e)
        { 
           this.UpdateListView();//更新listview显示内容
           this.Xflist();
        }
                   private void Xflist()
        {
            
            for (int i = 0; i < this.listView2.Items.Count;i++)
            {
                
                if (this.listView2.Items[i].Selected == true)
                {
                    
                    this.selectStr1 = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems[0].Text.ToString() + "'";
                    this.sqlCommand1.CommandText = this.selectStr1;
                    break;
                }
                
                    
            }                   
                    
                    try
                    {
                        
                       
                        if (this.sqlConnection1.State == ConnectionState.Closed) this.sqlConnection1.Open(); //如果connection1关闭就打开
                       this.SqlDataReader1=this.sqlCommand1.ExecuteReader();  //用sqldatareadrer来读取数据库中的内容
                        while (this.SqlDataReader1.Read())
                        {
                            ListViewItem li = new ListViewItem();//生成新的listview的item
                            li.SubItems.Clear();//消除所有列的内容
                            li.SubItems[0].Text = SqlDataReader1["Ctid"].ToString();//给新记录第1列添加餐台号内容
                            li.SubItems.Add(SqlDataReader1["Xfitem"].ToString());
                            li.SubItems.Add(SqlDataReader1["Dj"].ToString());//给新记录第2列添加单价
                            li.SubItems.Add(SqlDataReader1["Dzbl"].ToString());//给新记录第3添加单价
                            li.SubItems.Add(SqlDataReader1["Sl"].ToString());//给新记录第4列添加数量
                            li.SubItems.Add(SqlDataReader1["Money"].ToString());
                            li.SubItems.Add(SqlDataReader1["FUs"].ToString());
                            li.SubItems.Add(SqlDataReader1["Bz"].ToString());
                            this.listView1.Items.Add(li);//把新记录添加到listview1中去                        }
                    }                    catch (System.Exception E)
                    {
                        MessageBox.Show(E.ToString());
                    }
                    finally
                    {                        this.sqlConnection1.Close();
                    }          
        }
           
           
  }    
}

Answer 18

你的代码有问题，首先方法Xflist()不应该再form_load事件中调用，这样在窗体加载的时候，就运行了，而这个时候this.listView2.Items[i].Selected == true 这条语句永远为false， 也就是说if语句块压根就不会被执行，你的commandText当然就不会被赋值了。 你应该采用的是使用listview2的SelectedIndexChanged事件 在这个事件当中调用你的那个方法，并且你的方法写的太过笨重了，这个你可以考虑一下 缩减一下，因为你可以直接得到listView2的selectedItem的所以没有必要使用if语句for 语句 
还有就是上边阁楼提到的 你在使用commandText之前又将其置空了，这样这个dommandText当然始终是null 你的程序就肯定报错了

Answer 19

namespace CanYinManager 
{ 
    public partial class FormMain : Form 
    { 
        private string selectStr1;         private SqlConnection sqlConnection1 = null; 
        private SqlCommand sqlCommand1 = null; 
      private SqlDataReader SqlDataReader1 = null; 
public FormMain() 
        { 
            //在构造函数中为变量赋值             InitializeComponent();//系统初始函数 
            this.sqlConnection1 = new SqlConnection(CanYinManager.DataLevel.Connection.ConnString); 
            this.sqlCommand1 = new SqlCommand(); 
            this.sqlCommand1.Connection = this.sqlConnection1; 
        private void FormMain_Load(object sender, EventArgs e) 
        { 
          this.UpdateListView();//更新listview显示内容 
          this.Xflist(); //这个方法这里调用肯定会出错原因看代码红色部分 
        } 
                  private void Xflist() 
        { 
            
            for (int i = 0; i < this.listView2.Items.Count;i++) 
            { 
                
                if (this.listView2.Items[i].Selected == true) //你肯定这条语句始终是false
                { 
                    
                    this.selectStr1 = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems [0].Text.ToString() + "'"; 
                    this.sqlCommand1.CommandText = this.selectStr1; 
                    break; 
                } 
                
                    
            }                   
                    
                    try 
                    { 
                        
                      
                        if (this.sqlConnection1.State == ConnectionState.Closed) this.sqlConnection1.Open(); //如果 connection1关闭就打开 
                      this.SqlDataReader1=this.sqlCommand1.ExecuteReader();  //用sqldatareadrer来读取数据库中的内容 
                        while (this.SqlDataReader1.Read()) 
                        { 
                            ListViewItem li = new ListViewItem();//生成新的listview的item 
                            li.SubItems.Clear();//消除所有列的内容 
                            li.SubItems[0].Text = SqlDataReader1["Ctid"].ToString();//给新记录第1列添加餐台号内容 
                            li.SubItems.Add(SqlDataReader1["Xfitem"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["Dj"].ToString());//给新记录第2列添加单价 
                            li.SubItems.Add(SqlDataReader1["Dzbl"].ToString());//给新记录第3添加单价 
                            li.SubItems.Add(SqlDataReader1["Sl"].ToString());//给新记录第4列添加数量 
                            li.SubItems.Add(SqlDataReader1["Money"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["FUs"].ToString()); 
                            li.SubItems.Add(SqlDataReader1["Bz"].ToString()); 
                            this.listView1.Items.Add(li);//把新记录添加到listview1中去                         } 
                    }                     catch (System.Exception E) 
                    { 
                        MessageBox.Show(E.ToString()); 
                    } 
                    finally 
                    {                         this.sqlConnection1.Close(); 
                    }           
        } 
          
          
  }     
}