DevExpress LookUpEdit 初始化（数据加载） 底层类

（1）三个效果

  1>传的参数较多，对数据表无要求，但可以设置下拉列的宽度和标题

      2>传的参数很少，对数据表有要求(必须是处理好的)

      3>传的参数一般，对数据表无要求，但不可以设置下拉列的宽度和标题

1）

2）

3）

（2）后台代码

底层类：

  /// <summary>
        /// 初始化LookUpEdit控件 (加载数据表中的一列或多列，且显示下拉列标题，可以设置下拉列的宽度)
        /// </summary>
        /// <param name="lookUpEdit">空间名称</param>
        /// <param name="fields">下拉要显示的列</param>
        /// <param name="captions">下拉要显示的列标题</param>
        /// <param name="widths">下拉显示列的宽度  如果null 宽度为系统默认 </param>
        /// <param name="dt">绑定的数据表</param>
        /// <param name="valueMember">绑定列</param>
        /// <param name="displayMember">显示列</param>
        /// <param name="dropDownRows">下拉最多显示个数 如果为0，显示全部</param>
        public static void InitLookUpEdit(DevExpress.XtraEditors.LookUpEdit lookUpEdit,
           string[] fields, string[] captions, int[] widths,
           DataTable dt, string valueMember, string displayMember, int dropDownRows)
        {
            lookUpEdit.Properties.NullText = "---请选择---";
            lookUpEdit.Properties.Columns.Clear();
            if (fields.Length != captions.Length)
            {
                return;
            }
            for (int i = 0; i < fields.Length; i++)
            {
                if (widths != null)
                {
                    if (fields.Length != widths.Length)
                    {
                        return;
                    }
                    lookUpEdit.Properties.Columns.Add(new DevExpress.XtraEditors.Controls.LookUpColumnInfo(fields[i], widths[i], captions[i]));
                    lookUpEdit.Properties.Columns[i].Visible = widths[i] == 0 ? false : true;
                }
                else
                {
                    lookUpEdit.Properties.Columns.Add(new DevExpress.XtraEditors.Controls.LookUpColumnInfo(fields[i], captions[i]));
                }
                lookUpEdit.Properties.Columns[i].Alignment = DevExpress.Utils.HorzAlignment.Center;

            }

            if (widths == null)
                lookUpEdit.Properties.Columns[valueMember].Visible = false;

            lookUpEdit.Properties.DataSource = dt;
            lookUpEdit.Properties.ValueMember = valueMember;
            lookUpEdit.Properties.DisplayMember = displayMember;
            lookUpEdit.Properties.ShowHeader = true;
            lookUpEdit.Properties.ShowFooter = false;
            if (dropDownRows == 0)
            {
                lookUpEdit.Properties.DropDownRows = dt.Rows.Count + 1;
            }
            else
            {
                lookUpEdit.Properties.DropDownRows = dt.Rows.Count > dropDownRows ? dropDownRows : dt.Rows.Count;
            }
        }

        /// <summary>
        /// 初始化LookUpEdit控件 (下拉加载数据表中的所有列，且不显示下拉列标题、不设置宽度)
        /// </summary>
        /// <param name="lookUpEdit">控件名称</param>
        /// <param name="dt">绑定的数据表</param>
        /// <param name="valueMember">绑定列</param>
        /// <param name="displayMember">显示列</param>
        /// <param name="dropDownRows">下拉最多显示个数 如果为0，显示全部</param>
        public static void InitLookUpEdit(DevExpress.XtraEditors.LookUpEdit lookUpEdit,
          DataTable dt, string valueMember, string displayMember, int dropDownRows)
        {
            if (!dt.Columns.Contains(valueMember) && dt.Columns.Contains(displayMember))
            {
                return;
            }
            lookUpEdit.Properties.NullText = "---请选择---";
            lookUpEdit.Properties.Columns.Clear();

            foreach (DataColumn col in dt.Columns)
                lookUpEdit.Properties.Columns.Add(new DevExpress.XtraEditors.Controls.LookUpColumnInfo(col.ColumnName));

            lookUpEdit.Properties.DataSource = dt;

            lookUpEdit.Properties.Columns[valueMember].Visible = false;

            lookUpEdit.Properties.ValueMember = valueMember;
            lookUpEdit.Properties.DisplayMember = displayMember;
            lookUpEdit.Properties.ShowHeader = false;
            lookUpEdit.Properties.ShowFooter = false;
            if (dropDownRows == 0)
            {
                lookUpEdit.Properties.DropDownRows = dt.Rows.Count;
            }
            else
            {
                lookUpEdit.Properties.DropDownRows = dt.Rows.Count > dropDownRows ? dropDownRows : dt.Rows.Count;
            }
        }

        /// <summary>
        /// 初始化LookUpEdit控件 (下拉加载数据表中一列或多列，且不显示下拉列标题、不设置宽度)
        /// </summary>
        /// <param name="lookUpEdit">控件名称</param>
        /// <param name="dt">绑定的数据表</param>
        /// <param name="fields">下拉要显示的列(要包含绑定列)</param>
        /// <param name="valueMember">绑定列</param>
        /// <param name="displayMember">显示列</param>
        /// <param name="dropDownRows">下拉最多显示个数 如果为0，显示全部</param>
        public static void InitLookUpEdit(DevExpress.XtraEditors.LookUpEdit lookUpEdit,
            DataTable dt, string[] fields, string valueMember, string displayMember, int dropDownRows)
        {
            //数据表中是否存在fields的列
            if (fields != null)
            {
                for (int i = 0; i < fields.Length; i++)
                {
                    if (!dt.Columns.Contains(fields[i]))
                    {
                        MessageBox.Show("LookUpEdit控件 列名不在数据表中");
                        return;
                    }
                }
            }

            //过滤列 且去掉重复
            DataView dv = new DataView(dt);
            dt = dv.ToTable(true, fields);

            InitLookUpEdit(lookUpEdit, dt, valueMember, displayMember, dropDownRows);
        }

调用：

 //显示特定列 设置下拉列标题和宽度
            InitLookUpEdit(lookUpEdit1,
                new string[] { "Stu_Number", "Stu_Name" },
                new string[] { "学号", "姓名" },
                new int[] { 50, 80 },
                dt, "Stu_ID", "Stu_Name", 5);

            //显示全部列 不可以设置标题和宽度
            InitLookUpEdit(lookUpEdit2, dt, "Stu_ID", "Stu_Name", 5);

            //显示特定列 不可以设置标题和宽度
            InitLookUpEdit(lookUpEdit3, dt, new string[] { "Stu_Number", "Stu_Name", "Stu_ID" }, "Stu_ID", "Stu_Name", 5);

备注(常用)：

//总宽度
            lookUpEdit1.Properties.PopupWidth = lookUpEdit1.Width;
            //默认选择第一项 ,如果 =-1 显示NullText
            lookUpEdit1.ItemIndex = 0;
            //自适应宽度
            lookUpEdit1.Properties.BestFitMode = DevExpress.XtraEditors.Controls.BestFitMode.BestFitResizePopup;
            //下拉列表个数
            lookUpEdit1.Properties.DropDownRows = dt.Rows.Count;
         
            //列格式
            lookUpEdit1.Properties.Columns[0].FormatString = "000000";
            //列文字居中
            lookUpEdit1.Properties.Columns[0].Alignment = DevExpress.Utils.HorzAlignment.Center;

//显示的值 dispalyMember
            string str1 = lookUpEdit1.Text;
            //绑定的值 ValueMember
            string str2 = lookUpEdit1.EditValue.ToString();

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