vb.net 如何添加到 StringBuilder？
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How to prepend to a StringBuilder?
提问by Amaynut
VB.NET have a method, just like java, to append to an object of type StringBuilderBut can I prepend to this object (I mean a add some string before the stringbuilder value, not after). Here is my code:
VB.NET 有一个方法，就像 java 一样，可以附加到StringBuilder类型的对象， 但是我可以附加到这个对象吗（我的意思是在 stringbuilder 值之前添加一些字符串，而不是之后）。这是我的代码：
'Declare an array
Dim IntegerList() = {24, 12, 34, 42}
Dim ArrayBefore As New StringBuilder()
Dim ArrayAfterRedim As New StringBuilder()
ArrayBefore.Append("{")
For i As Integer = IntegerList.GetLowerBound(0) To IntegerList.GetUpperBound(0)
ArrayBefore.Append(IntegerList(i) & ", ")
Next
' Close the string
ArrayBefore.Append("}")
'Redimension the array (increasing the size by one to five elements)
'ReDim IntegerList(4)
'Redimension the array and preserve its contents
ReDim Preserve IntegerList(4)
' print the new redimesioned array
ArrayAfterRedim.Append("{")
For i As Integer = IntegerList.GetLowerBound(0) To IntegerList.GetUpperBound(0)
ArrayAfterRedim.Append(IntegerList(i) & ", ")
Next
' Close the string
ArrayAfterRedim.Append("}")
' Display the two arrays
lstRandomList.Items.Add("The array before: ")
lstRandomList.Items.Add(ArrayBefore)
lstRandomList.Items.Add("The array after: ")
lstRandomList.Items.Add(ArrayAfterRedim)
If you look at the last 4 lines of my code, I want to add the text just before the string builder all in one line in my list box control. So instead of this:
如果您查看我的代码的最后 4 行，我想在我的列表框控件中的一行中在字符串生成器之前添加文本。所以而不是这个：
lstRandomList.Items.Add("The array before: ")
lstRandomList.Items.Add(ArrayBefore)
I want to have something like this:
我想要这样的东西：
lstRandomList.Items.Add("The array before: " & ArrayBefore)
回答by Mark
You can use StringBuilder.Insertto prepend to the string builder:
您可以使用StringBuilder.Insert预先添加到字符串生成器：
Dim sb = New StringBuilder()
sb.Append("World")
sb.Insert(0, "Hello, ")
Console.WriteLine(sb.ToString())
This outputs:
这输出：
Hello, World
EDIT
编辑
Oops, noticed @dbasnett said the same in a comment...
糟糕，注意到@dbasnett 在评论中说了同样的话......
回答by Luke
You can append your StringBuilder(after converting it to a string) to a new StringBuildercontaining the string you wish to prepend. The result is effectively the same as prepending, it just requires a new StringBuilder.
您可以将您的StringBuilder（将其转换为字符串后）附加到StringBuilder包含您希望添加的字符串的新字符串。结果实际上与前置相同，它只需要一个新的StringBuilder.
回答by Enigmativity
Your code seems like a lot of overkill to use StringBuilderwith those Forloops.
StringBuilder与这些For循环一起使用您的代码似乎有些矫枉过正。
Why not do this?
为什么不这样做？
Dim IntegerList() = {24, 12, 34, 42}
lstRandomList.Items.Add("The array before: ")
lstRandomList.Items.Add(String.Format("{{{0}}}", String.Join(", ", IntegerList)))
ReDim Preserve IntegerList(4)
lstRandomList.Items.Add("The array after: ")
lstRandomList.Items.Add(String.Format("{{{0}}}", String.Join(", ", IntegerList)))
Job done. Much simpler code.
任务完成。更简单的代码。
