关于vb.netrtrim的信息

vb.net 里的substring()作用

substring 就是对一个指定的字符窜进行字符窜截取的方法。

运用的形式差不多如下：

截取后的字符窜 = 指定字符窜.substring（开始截取位置[第一位从0开始],截取长度）

Dim str As String = "dsk_cy"

Dim resultStr As String = str.substring(0,2)'截取最左边的两个字符 即 resultStr = “ds”

Dim reulst As String = str.substring(1,2) '截取从最左边数第二位开始的两个字符 即 result = “sk”

希望对你有帮助！

相关问答

Q1: VB.NET关键字上色/高亮问题。

Private Sub RichTextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RichTextBox1.TextChanged

Dim pos = RichTextBox1.SelectionStart

Dim i As String = Regex.Matches(RichTextBox1.Text, "\bDim\b").ToString

RichTextBox1.SelectAll

RichTextBox1.SelectionColor = Color.Black

If Regex.IsMatch(RichTextBox1.Text, "\bDim\b") = True Then

For Each mat As Match In Regex.Matches(RichTextBox1.Text, "\bDim\b")

RichTextBox1.SelectionStart = mat.Index

RichTextBox1.SelectionLength = mat.Length

RichTextBox1.SelectionColor = Color.YellowGreen

Next

End If

RichTextBox1.SelectionStart = pos

RichTextBox1.SelectionLength = 0

End Sub

我做了一个更详细的正则：

Friend Keys As String =

"\b(#Const|#If|Then|#Else|#Region|Delegate|Namespace|Class|End|Firend|Partial|Module|Interface|Enum|Shared|Overrides|Overloads|Structure|Let|Const|Dim|As|Private|Public|New|Static|Option|Private|Module|IsArray|IsDate|IsEmpty|IsError|IsMissing|IsNull|IsNumeric|IsObject|TypeName|VarType|Me|Option|Explicit|Mod|Like|Is|Not|And|Or|Xor|Eqv|Imp|Clear|Error|Raise|Error|Err|CVErr|On|Error|Resume|IsError|Collection|Add|Remove|Item|DDB|SLN|SYD|FV|Rate|IRR|MIRR|NPer|IPmt|Pmt|PPmt|NPV|PV|Do|Loop|For|Next|For|Each|Next|While|Wend|With|Choose|If|Then|Else|Select|Case|Switch|Call|Function|Property|Get|Property|Let|Property|Set|Sub|Date|Now|Time|DateAdd|DateDiff|DatePart|DateSerial|DateValue|TimeSerial|TimeValue|Date|Time|Timer|CBool|CByte|CCur|CDate|CDbl|CDec|CInt|CLng|CSng|CStr|CVar|CVErr|Fix|Int|Boolean|Byte|Currency|Date|Double|Integer|Long|Object|Single|String|Object|Atn|Cos|Sin|Tan|Exp|Log|Sqr|Randomize|Rnd|Abs|Sgn|Fix|Int|IsArray|Array|Option|Base|Dim|Private|Public|ReDim|Static|LBound|UBound|Erase|ReDim|DeleteSetting|GetSetting|GetAllSettings|SaveSetting|Chr|Format|LCase|UCase|DateSerial|DateValue|Hex|Oct|Format|Str|CBool|CByte|CCur|CDate|CDbl|CDec|CInt|CLng|CSng|CStr|CVar|CVErr|Fix|Int|Day|Month|Weekday|Year|Hour|Minute|Second|Asc|Val|TimeSerial|TimeValue|StrComp|StrConv|Format|LCase|UCase|Space|String|Len|Format|LSet|RSet|InStr|Left|LTrim|Mid|Right|RTrim|Trim|Option|Compare|Asc|Chr|AppActivate|Shell|SendKeys|Beep|Command)\b"

Q2: 关于VB.net取整的问题

double是双精度 有效数值位52位 表示成指数的形式 即指数11位 即表示成

所以180.89305用2进制表示是10110100.1110010010011110111011001011111110110001010110110101

即

180.89305在double中存在的实际数值是

1.01101001110010010011110111011001011111110110001010110110101 *2^7

取小数点后 52位有效值后 等于10进制的180.893049999999998

所及加最后变成了 1808930.99999999998

第一次当然输出近似值1808931

第二次int函数去掉了小数点后的数int就是只取整数的部位的不是四舍五入 所以少了1