縮短我的ElseIf聲明。怎麼樣？

Question

我在這裏有一些我想知道的，我希望每個人都可以幫助我。所以這裏是我的問題，我怎樣才能縮短我的代碼。 :)

If MetroTextBox1.Text = "" Then 
      If MetroCheckBox1.Checked = True And MetroCheckBox2.Checked = False Then 
       query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where dresigned is null and " + 
         " (id like '%" & MetroTextBox1.Text & "%' or fname like '%" & MetroTextBox1.Text & "%' or mname like '%" & MetroTextBox1.Text & "%' or lname like '%" & MetroTextBox1.Text & "%' or dept like '%" & MetroTextBox1.Text & "%') " 
       dt = c.GetDataTable(query) 
      ElseIf MetroCheckBox2.Checked = True And MetroCheckBox1.Checked = False Then 
       query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where dresigned is not null and " + 
         " (id like '%" & MetroTextBox1.Text & "%' or fname like '%" & MetroTextBox1.Text & "%' or mname like '%" & MetroTextBox1.Text & "%' or lname like '%" & MetroTextBox1.Text & "%' or dept like '%" & MetroTextBox1.Text & "%') " 
       dt = c.GetDataTable(query) 
      ElseIf MetroCheckBox1.Checked = True And MetroCheckBox2.Checked = True Then 
       query = "select id, fname, mname, lname, dept, salary from tbl_Employee" + 
         " where id like '%" & MetroTextBox1.Text & "%' or fname like '%" & MetroTextBox1.Text & "%' or mname like '%" & MetroTextBox1.Text & "%' or lname like '%" & MetroTextBox1.Text & "%' or dept like '%" & MetroTextBox1.Text & "%' " 
       dt = c.GetDataTable(query) 
      End If 
     ElseIf MetroTextBox1.Text <> "" Then 
      If MetroCheckBox1.Checked = True And MetroCheckBox2.Checked = False Then 
       query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where dresigned is null and " + 
         " (id like '%" & MetroTextBox1.Text & "%' or fname like '%" & MetroTextBox1.Text & "%' or mname like '%" & MetroTextBox1.Text & "%' or lname like '%" & MetroTextBox1.Text & "%' or dept like '%" & MetroTextBox1.Text & "%') " 
       dt = c.GetDataTable(query) 
      ElseIf MetroCheckBox2.Checked = True And MetroCheckBox1.Checked = False Then 
       query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where dresigned is not null and " + 
         " (id like '%" & MetroTextBox1.Text & "%' or fname like '%" & MetroTextBox1.Text & "%' or mname like '%" & MetroTextBox1.Text & "%' or lname like '%" & MetroTextBox1.Text & "%' or dept like '%" & MetroTextBox1.Text & "%') " 
       dt = c.GetDataTable(query) 
      ElseIf MetroCheckBox1.Checked = True And MetroCheckBox2.Checked = True Then 
       query = "select id, fname, mname, lname, dept, salary from tbl_Employee" + 
         " where id like '%" & MetroTextBox1.Text & "%' or fname like '%" & MetroTextBox1.Text & "%' or mname like '%" & MetroTextBox1.Text & "%' or lname like '%" & MetroTextBox1.Text & "%' or dept like '%" & MetroTextBox1.Text & "%' " 
       dt = c.GetDataTable(query) 
      End If 
     Else 
      query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where id = ''" 
      dt = c.GetDataTable(query) 
     End If 

Answer 1

由於問題是關於縮短代碼，方法如下：

query = " (id like '%" & MetroTextBox1.Text & "%' or fname like '%" & MetroTextBox1.Text & "%' or mname like '%" & MetroTextBox1.Text & "%' or lname like '%" & MetroTextBox1.Text & "%' or dept like '%" & MetroTextBox1.Text & "%')" 
If MetroTextBox1.Text = "" Then 
    If MetroCheckBox1.Checked = True And MetroCheckBox2.Checked = False Then 
     query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where dresigned is null and" + query 
    ElseIf MetroCheckBox2.Checked = True And MetroCheckBox1.Checked = False Then 
     query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where dresigned is not null and" + query 
    ElseIf MetroCheckBox1.Checked = True And MetroCheckBox2.Checked = True Then 
     query = "select id, fname, mname, lname, dept, salary from tbl_Employee where" + query 
    End If 
ElseIf MetroTextBox1.Text <> "" Then 
    If MetroCheckBox1.Checked = True And MetroCheckBox2.Checked = False Then 
     query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where dresigned is null and" + query 
    ElseIf MetroCheckBox2.Checked = True And MetroCheckBox1.Checked = False Then 
     query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where dresigned is not null and" + query 
    ElseIf MetroCheckBox1.Checked = True And MetroCheckBox2.Checked = True Then 
     query = "select id, fname, mname, lname, dept, salary from tbl_Employee where" + query 
    End If 
Else 
    query = "select id, fname, mname, lname, dept, salary, ' ' as lengthservice from tbl_Employee where id = ''" 
End If 
dt = c.GetDataTable(query) 

Answer 2

這是更好的（短）代碼：

Dim t1 As String = MetroTextBox1.Text 
Dim c1 As Boolean = MetroCheckBox1.Checked 
Dim c2 As Boolean = MetroCheckBox2.Checked 

Dim a, b As String 
a = "select id, fname, mname, lname, dept, salary" 
b = "(id like '%" & t1 & "%' or fname like '%" & t1 & "%' or mname like '%" & t1 & "%' or lname like '%" & t1 & "%' or dept like '%" & t1 & "%') " 

If c1 And Not c2 Then 
    query = a + ", ' ' as lengthservice from tbl_Employee where dresigned is null and " + b 

ElseIf c2 And Not c1 Then 
    query = a + ", ' ' as lengthservice from tbl_Employee where dresigned is not null and " + b 

Else 'If c1 And c2 Then 
    query = a + " from tbl_Employee where " + b 

End If 

dt = c.GetDataTable(query) 

（很明顯的是，最終Else永遠不會被調用，因爲始終MetroTextBox1.Text =「」或MetroTextBox1.Text <>「」將爲真）。

但是，這裏有一個註釋。當MetroTextBox1.Text =「」時，b中指定的條件變爲(id like '%%' or fname like '%%' or ...)，類似於where 1=1，可以從查詢中刪除該條件。但它不是基於您的原始代碼。如果你願意，我可以給修改後的代碼

Answer 3

由於問題是關於縮短代碼，這裏是沒有If語句簡短的解決方案

Dim query As String = 
    "SELECT id, fname, mname, lname, dept, salary, ' ' AS lengthservice 
    FROM tbl_Employee 
    WHERE (id LIKE @MetroTextBox1 
     OR fname LIKE '%" & MetroTextBox1.Text & "%' 
     OR mname LIKE '%" & MetroTextBox1.Text & "%' 
     OR lname LIKE '%" & MetroTextBox1.Text & "%' 
     OR dept LIKE '%" & MetroTextBox1.Text & "%')" 

Dim condition As New Dictionary(Of Byte, String) From 
{ 
    {0, ""}, 'You don't have result for case False, False 
    {1, " AND dresigned IS NULL"}, 'If MetroCheckBox1.Checked = True 
    {2, " AND dresigned IS NOT NULL"}, 'If MetroCheckBox2.Checked = True 
    {3, ""} 'Both Checkboxes are checked 
} 

Dim checkBox1 As Byte = Convert.ToByte(MetroCheckBox1) 
Dim checkBox2 As Byte = Convert.ToByte(MetroCheckBox2) << 1 
Dim selection As Byte = checkBox1 Or checkBox2 

query = query & condition(selection) 

dt = c.GetDataTable(query) 

而且很重要的：使用SqlParameters傳遞值查詢

參數可以幫助您避免Sql注入問題，也可以讓您的查詢的出價更快。