commandText属性尚未初始化是什么原因啊？！

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，可是，系统总提示我commandText属性尚未初始化，之前我已经初始化了啊？！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 
                    { 
                         
                        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

private void Xflist() 
        { 
          
            this.sqlCommand1.CommandText="";
            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 2

不行啊？！我加了这一行 this.sqlCommand1.CommandText=""; 　　　还是出现这个错误

Answer 3

有个问题明确一下，楼主这个方法是在什么情况下执行？
 if (this.listView2.Items[i].Selected == true) 
这句能返回true吗？如果不能肯定不会给this.sqlCommand1.CommandText赋值
请在后面break;这行是下断点看看

Answer 4

            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;  
                } 
                
                    
            } 
如果你的listView2选中的Items是-1时就没有值啦。
另外就是sqlCommand1有实例化吗？
有没有sqlCommand1=new SqlCommand(……)或者sqlCommand1=sqlConnection1.CreateCommand()?

Answer 5

我这个方法是在窗体的load事件中加载进去的啊！ if (this.listView2.Items[i].Selected == true) 是判断是否选中一行，我在IF语句体中加了一个break，可还是不行啊？！另外listView2选中的Items怎么可能是-1呢，我listview2中是有记录的

Answer 6

sqlCommand1=new SqlCommand；之类的初始化我都已经做了，可是还是不行，真奇怪　

Answer 7

this.selectStr1是一个控件？
如果赋值的话，应该赋给this.selectStr1的文本吧

Answer 8

  this.selectStr1 = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems[0].Text.ToString() + "'"; 
this.sqlCommand1.CommandText = this.selectStr1; 
为什么要经过this.selectStr1之后再赋值给CommandText呢？不可以直接
this.sqlCommand1.CommandText = "SELECT *  FROM Xfxm WHERE  Ctid='" + this.listView2.Items[i].SubItems[0].Text.ToString() + "'"; 
这样有什么问题？

Answer 9

 可以直接赋值给CommandText  啊     你还是用断点 调试在看错误在那 ，  连接打开是否有问题， 命令对不  

Answer 10

完整代码是这样的：
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 11

listView2默认是不选中任何项的。。所以this.sqlCommand1.CommandText 没有初始化。