[學習] Access FULL JOIN 解決方案

問題：
我們來作一個 FULL JOIN 查詢：

解決：
LEFT JOIN, RIGHT JOIN Operations (Microsoft Access SQL)
[数据库] ACCESS中不支持FULL JOIN的解决方案
Full Outer Join in MS Access

[除錯] DataGridView RowValidating事件, 當按Escape取消時, 不要引發該事件...

as title...

參考：
Escaping DataGridView Row creation fires RowValidating. How to avoid this?

1)

private void dataGridView1_KeyDown(object sender, KeyEventArgs e) 

{ 

     if (e.KeyCode == Keys.Escape) 

     { 

          this.dataGridView1.RowValidating -= 

               new System.Windows.Forms.DataGridViewCellCancelEventHandler(this.dataGridView1_RowValidating); 

     } 

     this.dataGridView1.RowValidating += 

          new System.Windows.Forms.DataGridViewCellCancelEventHandler(this.dataGridView1_RowValidating); 

}

2)

if (!view.IsCurrentRowDirty ) return; 

[學習] Subquery using Composite Key (組合鍵子查詢)

SQL：


參考：
Subquery using Composite Key
WHERE col1,col2 IN (…) [SQL subquery using composite primary key]

[學習] 在C#實現VB函式【IsNumeric】

【CODE】

        static bool IsNumeric(object Expression)
        {
            // Variable to collect the Return value of the TryParse method.
            bool isNum;
            // Define variable to collect out parameter of the TryParse method. If the conversion fails, the out parameter is zero.
            double retNum;
            // The TryParse method converts a string in a specified style and culture-specific format to its double-precision floating point number equivalent.
            // The TryParse method does not generate an exception if the conversion fails. If the conversion passes, True is returned. If it does not, False is returned.
            isNum = Double.TryParse(Convert.ToString(Expression), System.Globalization.NumberStyles.Any, System.Globalization.NumberFormatInfo.InvariantInfo, out retNum);
            return isNum;
        }

【CODE】

        public static bool IsNum(String str)
        {
            for (int i = 0; i < str.Length; i++)
            {
                if (str[i] < '0' || str[i] > '9')
                    return false;
            }
            return true;
        }

參考：
判断一个字符串是否全是数字的多种方法及其性能比较（C#实现）
[C#]IsNumeric 判斷是否為數值
[C#]數值驗證 IsNumeric
C# Equivalent of VB's IsNumeric()
C# IsNumeric
C#的判斷是否為數字，難道只能用Try、Catch嗎?..沒有VB.NET的IsNumeric可用嗎

[學習] MenuStrip 合併菜單

除錯：
mdiParent的MenuStrip若設定 Ctrl-X 等文字編輯快捷鍵時，當mdiChildren無MenuStrip設定...
則該視窗的 RichTextbox 會因 mdiParent 的快捷鍵設定而失效...

解決：
直接在mdiChildren設定MenuStrip並設定與mdiParent第一格相同的名稱，
並將該格enable設為false，MergeAction=Replace，MergeIndex設為要取代MenuStrip某欄的Index
無需再設定任何快捷鍵...
則RichTextbox的文字編輯快捷鍵立即復活...

參考：
【转】menustrip控件中mergeaction属性的作用
在 Windows 窗体 MenuStrip 控件中合并菜单项
合併 Windows Form MenuStrip 控制項中的功能表項目

[學習] 從一個datatable找某column的最大值

運用linq + lambda
或直接用datatable的彙總函式

e.Row.Cells("收退序號").Value = If(dgv_單據明細.Rows.Count > 1,
     tbl.Compute("max(收退序號)",
     "管理模式編號=" & cbo_管理模式編號.SelectedValue & _
     " AND 收退單號='" & txt_收退單號.Text & "'") + 1,
     1)

參考：
從查詢中建立 DataTable (LINQ to DataSet)
單一資料表查詢 (LINQ to DataSet)
DataTable: Get Max Value Using LINQ With Criteria Field (GroupBy)
How to select min and max values of a column in a datatable?
DataTable.Compute 方法

[學習] 當二個以上Combobox繫結相同來源時，若其中一個改變選項，則其它相同參考的Combobox不隨之改變....

程式：[用不同的BindingContext就好了]
        If MyUserProgInfo.frmLogin使用WebServices Then
            cbo_單據別1.DataSource = ws.ItemtblB備案手冊單據別基本資料表_GetMdl()
        Else
            cbo_單據別1.DataSource = New BLLMSSQL.BllBasicCtrlsSource().ItemtblB備案手冊單據別基本資料表
        End If
        cbo_單據別1.DisplayMember = "DisplayValue"
        cbo_單據別1.ValueMember = "單據別"

        cbo_單據別2.BindingContext = New BindingContext()
        cbo_單據別2.DataSource = cbo_單據別1.DataSource
        cbo_單據別2.DisplayMember = "DisplayValue"
        cbo_單據別2.ValueMember = "單據別"

參考：
WinForms ComboBox data binding gotcha
Multiple Combo Boxes With The Same Data Source (C#)

BindingContext 類別
关于控件使用DataBindings.Add方法进行简单绑定的问题

Bind multiple ComboBox to a single List - Issue: When I select an item, all combo boxes change

WinForms ComboBox data binding gotcha

WinForm数据绑定--BindingContext
How can i bind data to a datagridview combobox column?

You could create a BindingList<> object to hold your objects and then bind that list to the three controls. Then setting the BindingContexts to different objects would let the 3 controls have different positions with a single list.
  

public partial class Form1 : Form

  {

  public Form1()

  {

    InitializeComponent();

  }

 

  private void Form1_Load(object sender, EventArgs e)

  {

    BindingList<MyObject> list = new BindingList<MyObject>();

    list.Add(new MyObject("Ramya", 43));

    list.Add(new MyObject("Manju", 43));

    list.Add(new MyObject("Gulnus", 43));

    list.Add(new MyObject("Sona", 43));

 

    dataGridView1.DataSource = list;

    comboBox1.DataSource = list;

    comboBox1.DisplayMember = "Name";

    comboBox1.ValueMember = "Name";

 

    comboBox2.DataSource = list;

    comboBox2.DisplayMember = "Name";

    comboBox2.ValueMember = "Name";

 

    comboBox1.BindingContext = new BindingContext();

    comboBox2.BindingContext = new BindingContext();

    dataGridView1.BindingContext = new BindingContext();

 

  }

  }

 

  public class MyObject

  {

  private string mName;

  private int mAge;

 

  public MyObject(string s, int i)

  {

    mName = s;

    mAge = i;

  }

  public string Name

  {

    get { return mName; }

    set { mName = value; }

  }

  public int Age

  {

    get { return mAge; }

    set { mAge = value; }

  }

  public override string ToString()

  {

    return Name;

  }

  }