编写查询功能TextBox

主要是继承原有TextBox；追加编号内容（ValueText）和显示内容（DisplayText）；在编辑完成后查询数据库调出DisplayText（如：名称）；并显示在原TextBox中；当TextBox为编辑状态是显示ValueText(如：编号)

当然还可以进一步增强；如：增加对于的数据字典、增加DataRow所有数据（便于开发时根据记录集更新其他组件）等等

运行效果如下图

主要代码:

1.继承组件

public partial class TTextBox : Infragistics.Win.UltraWinEditors.UltraTextEditor

2.定义属性

        private string displayMember;
        public string DisplayMember { get { return displayMember; } set { displayMember = value; } }

        private string valueMember;
        public string ValueMember { get { return valueMember; } set { valueMember = value; } }


        private int max_Length;
        public int Max_Length { get { return max_Length; } set { max_Length = value; } }

3.原始原组件事件；并追加代码

 protected override void OnEndInit()
        {
            base.OnEndInit();
            max_Length = base.MaxLength;
            
        }

        protected override void OnBeforeEnterEditMode(CancelEventArgs e)
        {
            base.OnBeforeEnterEditMode(e);
            if (valueMember == null)
                valueMember = "";
            if (max_Length != null && max_Length != 0)
                base.MaxLength = max_Length;
            base.Value = valueMember;
         
             
        }
        protected override void OnEnter(EventArgs e)
        {
            base.OnEnter(e);
            base.SelectAll();
        }

        protected override void OnAfterExitEditMode(EventArgs e)
        {
            base.OnAfterExitEditMode(e);
            if (displayMember == null)
                displayMember = "";
            base.MaxLength = 0;
            base.Value = displayMember;
        }

protected override void OnValueChanged(EventArgs e)
        {
           
            base.OnValueChanged(e);
            if (base.Value == null)
                return;
            valueMember = base.Value.ToString();
            //maxLength = base.MaxLength;
            DisplayMember = GetValue("select Name from Table");            
            if (DisplayMember == "")
                valueMember = "";
            else
                DisplayMember = DisplayMember+ "(" + valueMember + ")";
        }

运行效果如下图: