I want to repeat .- 40 times and save it to a string using StringBuilder
Why does this not work?
string result = new StringBuilder("").Append(".-",0,40).ToString();
I know about other Solutions but i want to use StringBuilder
3 Answers
That method does not do what you think it does. The 2 int parameters specify the start index and length of the sub-string you want to append.
StringBuilder does have a method for what you want: It's called Insert:
sb.Insert(0, ".-", 40);
3 Comments
Dennis_E
Yes, it is the length. Methods like these are confusing. In some methods the 2nd int means the end index, in other methods it means the length. Edited.
juharr
Well most C# libraries go with start and length were as Java does the start and end. In this case it's even worse because they named the last argument
count.Dennis_E
@juharr
Parallel.ForEach for example uses start and end... I think I prefer that. "All numbers from 20 to 50" is clearer to me than "30 numbers starting from 20"StringBuilder sb = new StringBuilder();
for (int i = 0; i < 40; i++)
{
sb.Append(".-");
}
MessageBox.Show(sb.ToString());
answered Sep 7, 2016 at 12:21
Balagurunathan Marimuthu
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1 Comment
Adriano Repetti
Dumping code is seldom useful for OP and for future readers, I'd also explain why he has not to initialize StringBuilder with an empty string, why his solution with Append() is wrong and why he may want to set initial capacity to 80 and how this is different with Insert()...
If you want to repeat a string several times your options are:
1- Using a loop (as pointed by @Balagurunathan's answer)
2- For single characters you can use:
string result = new string('a', 10); //aaaaaaaaaa
For strings of more than one character:
string result = string.Join("", Enumerable.Repeat(".-", 5)) //.-.-.-.-.-
So I believe what you were trying to do was something along these lines:
string result = new StringBuilder().Append(string.Join("", Enumerable.Repeat(".-", 40))).ToString();
I would however stick to the for loop in terms of performance
Appendworks. You are telling it to append a substring not to repeat that string. Specifically the last argument is actually the length of the substring. They just gave it the unfortunate name ofcount.