combobox动态数据源，加载不到数据时报错

dong127 2012-04-13 06:27:01

功能需求是这样的：
根据输入的值在数据库中模糊查询匹配的数据，并显示在下拉框列表中，当有值可选时，自动打开下拉框，
除非选中下拉框中的某一个数据，否则要保持用户输入的数据不变





namespace WindowsFormsApplication1

{

    public partial class Form4 : Form

    {

        public Form4()

        {

            InitializeComponent();

            // 构造数据 

            loaddata();

        }

        // 构造数据源 

        private DataTable mdataSource = new DataTable();

        // 特殊出标志 

        private bool flag = false;

        private DataTable dtfliter = new DataTable();



        // 初始化数据 

        /// <summary> 

        /// 构造数据 

        /// </summary> 

        private void loaddata()

        {

            DataTable dt = new DataTable();

            dt.Columns.Add("name", typeof(string));

            dt.Columns.Add("value", typeof(string));

            DataRow dr0 = dt.NewRow();

            dr0["name"] = string.Empty;

            dr0["value"] = "0";

            dt.Rows.Add(dr0);

            DataRow dr1 = dt.NewRow();

            dr1["name"] = "1X#-100";

            dr1["value"] = "1X#-100";

            dt.Rows.Add(dr1);

            DataRow dr2 = dt.NewRow();

            dr2["name"] = "1X#-1200";

            dr2["value"] = "1X#-1200";

            dt.Rows.Add(dr2);

            DataRow dr3 = dt.NewRow();

            dr3["name"] = "abc";

            dr3["value"] = "3";

            dt.Rows.Add(dr3);



            DataRow dr4 = dt.NewRow();

            dr4["name"] = "time";

            dr4["value"] = "4";

            dt.Rows.Add(dr4);



            DataRow dr5 = dt.NewRow();

            dr5["name"] = "this is a max length string to test if the dropdownwith is autochange";

            dr5["value"] = "5";

            dt.Rows.Add(dr5);

            DataRow dr6 = dt.NewRow();

            dr6["name"] = "date";

            dr6["value"] = "6";

            dt.Rows.Add(dr6);

            DataRow dr7 = dt.NewRow();

            dr7["name"] = "time and date";

            dr7["value"] = "7";

            dt.Rows.Add(dr7);

            dt.AcceptChanges();

            mdataSource = dt;

            BindDate(mdataSource);

        }



        private void BindDate(DataTable dt)

        {

            this.comboBox1.DataSource = dt;

            this.comboBox1.DisplayMember = "name";

            this.comboBox1.ValueMember = "value";

 

            comboBox1.SuspendLayout();

        }





        /// <summary> 

        /// combobox 输入事件 

        /// </summary> 

        /// <param name="sender"></param> 

        /// <param name="e"></param> 

        private void comboBox1_KeyUp(object sender, KeyEventArgs e)

        {try{

            if (this.comboBox1.Text == string.Empty)

            {

                BindDate(mdataSource);

                this.comboBox1.Text = string.Empty;

                return;

            }

            flag = false;

            string str = this.comboBox1.Text;

            // 根据输入的值自带筛选 

            bool validate = Fillter(str);



            // 现实下拉框 

            this.comboBox1.DroppedDown = true;

            // 输入无效的数据 

            

                this.comboBox1.Text = str;

                if (comboBox1.Text != null && comboBox1.Text != string.Empty)

                {

                    // 获得光标位置 

                    this.comboBox1.SelectionStart = comboBox1.Text.Length;

                }

            



            // 现实鼠标 

            this.comboBox1.Cursor = Cursors.Default;

            }

            catch (Exception ex) {

                MessageBox.Show(ex.Message);

            }



        }



        /// <summary> 

        /// 筛选匹配的值 

        /// </summary> 

        /// <param name="str"></param> 

        private bool Fillter(string str)

        {

            bool isvalida = true;

            DataTable dt = mdataSource.Clone();

            // 循环筛选匹配的值       

            foreach (DataRow dr in mdataSource.Rows)

            {

                int i = -1;

                i = dr["name"].ToString().IndexOf(str.ToString());

                if (i > -1)

                {

                    DataRow newrow = dt.NewRow();

                    newrow.ItemArray = dr.ItemArray;

                    // 构造新的数据 

                    dt.Rows.Add(newrow);

                }



            }

            dt.AcceptChanges();

            BindDate(dt); 

            // 当为一条数据要特殊处理/不然光标返回有问题 

            if (dt.Rows.Count == 1)

            {

                // 特殊处理标志 

                flag = true;

                this.comboBox1.Text = str;// str 参数为输入的值;  

                int len = str.Length;

                

            }

            

            return isvalida;

        }



    }

}