Linq Join 方式

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// linq 正規 Join 方式 DataTable dt = (from l in db.Log join u in db.User on l.InsertUserId equals u.Id into lu from j1 in lu.DefaultIfEmpty() join i in db.Item on l.ItemId equals i.Id into li from j2 in li.DefaultIfEmpty() join it in db.ItemType on j2.ItemTypeId equals it.Id select new { Id = l.Id, 日期 = l.Date, 項目 = it.ItemTypeName + "-" + j2.ItemName, 價格 = l.Price, 人員 = j1.UserName, } ).ToDataTable(); // linq 非正規 Join 方式 DataTable dt = ( from l in db.Log from u in db.User from i in db.Item from it in db.ItemType where 1 == 1 && l.InsertUserId == u.Id && l.ItemId == i.Id && i.ItemTypeId == it.Id && (i.ItemName.Contains(Query) || it.ItemTypeName.Contains(Query)) select new { Id = l.Id, 日期 = l.Date, 項目 = it.ItemTypeName + "-" + i.ItemName, 價格 = l.Price, 人員 = u.UserName, } ).ToDataTable();

EventHandler 自訂事件

UserControl1.cs

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public partial class UserControl1 : UserControl { /// <summary> /// 建立事件處理 /// </summary> new public event EventHandler TextChanged; /// <summary> /// 事件處理函數 /// </summary> protected void OnTextChanged() { // 如果有建立事件監聽，則Invoke TextChanged?.Invoke(this.textBox1, new EventArgs()); } public UserControl1() { InitializeComponent(); } /// <summary> /// 使用者控制項 的 TextBox 預設 TextChanged 事件 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void textBox1_TextChanged(object sender, EventArgs e) { OnTextChanged(); } }

Form1.cs

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public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { // 針對使用者控制項新增自訂的 TextChanged 事件 this.userControl11.TextChanged += UserControl11_TextChanged; } /// <summary> /// 使用者控制項新增自訂的 TextChanged 事件處理函數 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void UserControl11_TextChanged(object sender, EventArgs e) { if (sender is TextBox) { TextBox tb = sender as TextBox; label1.Text = tb.Text; } } }