未处理的“System.NullReferenceException”类型的异常出现在 Relation.dll 中。

Question

 c#做控件库是出现的错误
代码如下：错误点是if (navigater.Position == 0) 请指教，谢谢！private void UserControl1_Load(object sender, EventArgs e)
        {
            getconn();
            string sql = "select*from Ontology_master";
            DataSet dt = new DataSet();
            SqlDataAdapter sda = new SqlDataAdapter(sql, conn);
           
            sda.Fill(dt, "Ontology_master");
            for (int i = 0; i < dt.Tables[0].Rows.Count; i++)
            {
                Label lb = GetLabel(i);
                if (lb != null)
                {                    if (navigater.Position == 0)
                    {
                        navigater.Position = navigater.Count - 1;                        lb.DataBindings.Add("Text", dt, "Ontology_master.name");
                    }
                    else
                    {
                        navigater.Position -= 1;
                        lb.DataBindings.Add("Text", dt, "Ontology_master.name");
                    }
                    
                }
                conn.Close();
            }
           
                   }

Answer 1

可是，我在开始已经 初始化了 
BindingManagerBase navigater;

Answer 2

我主要想实现将某一字段的所有值，分别显示在各个label中，一个lable显示一个值，如何实现啊！请帮帮我啊。我搞了几天了！都每个头绪

Answer 3

我写的全部代码如下：请高手指点一下!
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.IO;
using System.Data.SqlClient;
using System.Net;namespace Relation
{
    [Guid("7bf8de5d-f14e-4b92-bada-28309851552d")]
    public partial class UserControl1 : UserControl,IObjectSafety 
    {
         BindingManagerBase navigater;        SqlConnection conn = new SqlConnection();        public UserControl1()
        {
            InitializeComponent();
        }        public void GetInterfacceSafyOptions(Int32 riid, out Int32 pdwSupportedOptions, out Int32 pdwEnabledOptions)
        {
            // TODO:  添加 WebCamControl.GetInterfacceSafyOptions 实现 
            pdwSupportedOptions = 1;
            pdwEnabledOptions = 2;
        }        public void SetInterfaceSafetyOptions(Int32 riid, Int32 dwOptionsSetMask, Int32 dwEnabledOptions)
        {
            // TODO:  添加 WebCamControl.SetInterfaceSafetyOptions 实现             
        }
        public SqlConnection getconn()
        {
          
            conn.ConnectionString ="Data Source=PC4001\\SQLEXPRESS;Initial Catalog=webdata;User ID=sa;Password=123456";
            conn.Open();
            return conn;
        }        private Label GetLabel(int t)
        {
            int index = t;
            foreach (Control c in this.Controls)
            {
                if (c.Name == ("label" + index))
                {
                    return (Label)c;
                }
            }
            return null;
        }
        private void UserControl1_Load(object sender, EventArgs e)
        {
            getconn();
            string sql = "select*from Ontology_master";
            DataSet dt = new DataSet();
            SqlDataAdapter sda = new SqlDataAdapter(sql, conn);
           
            sda.Fill(dt, "Ontology_master");
            for (int i = 0; i < dt.Tables[0].Rows.Count; i++)
            {
                Label lb = GetLabel(i);
                if (lb != null)
                {                    if (navigater.Position == 0)
                    {
                        navigater.Position = navigater.Count - 1;                        lb.DataBindings.Add("Text", dt, "Ontology_master.name");
                    }
                    else
                    {
                        navigater.Position -= 1;
                        lb.DataBindings.Add("Text", dt, "Ontology_master.name");
                    }
                    
                }
                conn.Close();
            }
           
                   }    }
}

Answer 4

这个不是初始化  这个是声明
navigater=new ....()  才是初始化

Answer 5

请您帮帮我，我主要想实现将某一字段的所有值，分别显示在各个label中，一个lable显示一个值，如何实现啊！请帮帮我啊。我搞了几天了！都每个头绪 
这个应该如何实现？感激不尽！