StringBuilder and '+' operators

Question

I support this code here, which often has a pattern similar to the following:

StringBuilder result = new StringBuilder();

result.Append("{=" + field.Name + "={");

It seems like a lot of meaningless object construction is associated with this, and I want to rewrite this:

result.Append("{=").Append(field.Name).Append("={");

Is it true that the first version puts more strain on the GC? Or is there some kind of optimization in the C # compiler with string literals where string concatenation with string literals does not create temporary objects?

Answer 1

I agree with all the answers, but for me you need to understand the lines in C #, and they actually manipulate "under the covers"

StringBuilder , 5 . - , :

string a = b + c + d + e + f;

r = String.Concat(new String[5] { a, b, c, d, e });

.

, #:
http://ericlippert.com/2013/06/17/string-concatenation-behind-the-scenes-part-one/ http://ericlippert.com/2013/06/24/string-concatenation-behind-the-scenes-part-two/

Answer 2

. , . :

public static string BenchmarkMethod(Action method, int iterations)
{
    var watch = new Stopwatch();
    var results = new List<TimeSpan>(iterations);
    for (int iteration = 0; iteration < iterations; iteration++)
    {
    watch.Start();
    method();
    watch.Stop();
    results.Add(watch.Elapsed);
    watch.Reset();
    }

    var builder = new StringBuilder();
    builder.Append("Method benchmarked: ");
    builder.Append(method.Method.ReflectedType);
    builder.Append(".");
    builder.AppendLine(method.Method.Name);
    builder.Append("Average time in ticks: ");
    builder.AppendLine(results.Average(t => t.Ticks).ToString());

    return builder.ToString();
}

:

public static void StringConcatOperatorX8()
{
    var foo = strings[0] + strings[1] + strings[2] + strings[3] + strings[4] + strings[5] + strings[6] + strings[7] + strings[8];
}

public static void StringBuilderAppendsX8()
{
    var builder = new StringBuilder();
    builder.Append(strings[0]);
    builder.Append(strings[1]);
    builder.Append(strings[2]);
    builder.Append(strings[3]);
    builder.Append(strings[4]);
    builder.Append(strings[5]);
    builder.Append(strings[6]);
    builder.Append(strings[7]);
    builder.Append(strings[8]);

    var result = builder.ToString();
}

strings - , 9, 30

1 8 concats/appends. , 1 6, 3 10 000 .

UPDATE: (1 , ) . , StringBuilder - . 30 StringBuilder , +... , , , , .

: . + StringBuilder , . , StringBuilder:

public static void StringConcatAltOperatorX8()
{
    var foo = strings[0];
    foo += strings[1];
    foo += strings[2];
    foo += strings[3];
    foo += strings[4];
    foo += strings[5];
    foo += strings[6];
    foo += strings[7];
    foo += strings[8];
}

, 30 1 . , 5.809297 . 12.933227 . StringBuilder 11.27558 . . , .

Answer 3

, StringBuilder , String, . GC, , StringBuilder.

( ), , StringBuilder(int), .

, AppendFormat , :

result.Append("{=").Append(field.Name).Append("={");

:

result.AppendFormat("{{={0}={{", field.Name);

, , .

, result - ( ), String.Format("{{={0}={{", field.Name) String.Concat("{=", field.Name. "={"), StringBuilder. MSDN : " StringBuilder , String, String StringBuilder , . , , , , , . , StringBuilder ".