缩短我的ElseIf声明。怎么样？

Question

我在这里有一些我想知道的，我希望每个人都可以帮助我。所以这里是我的问题，我怎样才能缩短我的代码。 :)

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

由于问题是关于缩短代码，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

这是更好的（短）代码：

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) 

（很明显的是，最终Else永远不会被调用，因为始终MetroTextBox1.Text =“”或MetroTextBox1.Text <>“”将为真）。

但是，这里有一个注释。当MetroTextBox1.Text =“”时，b中指定的条件变为(id like '%%' or fname like '%%' or ...)，类似于where 1=1，可以从查询中删除该条件。但它不是基于您的原始代码。如果你愿意，我可以给修改后的代码

Answer 3

由于问题是关于缩短代码，这里是没有If语句简短的解决方案

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传递值查询

参数可以帮助您避免Sql注入问题，也可以让您的查询的出价更快。