My name
is
Jon Skeet

Multi line string literal format gives me error Input string was not in a correct format

I have the following variable:

var setting = 
$@"worker_processes     {{0}};
worker_rlimit_nofile    {{1}};
error_log               logs/{{2}} {{3}};

events
{{
    worker_connections {{4}};
    multi_accept {{5}};
}}";

When I do the following String.Format() operation on it:

return string.Format(setting,
    this.worker_processes,
    this.worker_rlimit_nofile,
    this.error_log_file,
    this.error_log_level,
    this.worker_connections
    this.multi_accept ? "on" : "off");

I get the following error: Input string was not in a correct format.

Any ideas?

EDIT - Fixed

Thanks to Jon Skeet, I have arrived at this solution without using String.Format():

return 
$@"worker_processes         { this.worker_processes };
    worker_rlimit_nofile    { this.worker_rlimit_nofile };
    error_log               logs/{ this.error_log_file } { this.error_log_level };

    events
    {{
        worker_connections { this.worker_connections };
        multi_accept { (this.multi_accept ? "on" : "off") };
    }}";

It's unclear exactly what's going on as there's version confusion, but I suspect you just want:

var setting = 
@"worker_processes     {0};
worker_rlimit_nofile    {1};
error_log               logs/{2} {3};

events
{{
    worker_connections {4};
    multi_accept {5};
}}";

Now the braces for the events block will still be escaped, but the rest will be treated as format specifiers.

Here's a full example:

using System;

class Test
{
    static void Main(string[] args)
    {
        var setting = 
@"worker_processes     {0};
worker_rlimit_nofile    {1};
error_log               logs/{2} {3};

events
{{
    worker_connections {4};
    multi_accept {5};
}}";
        string text = string.Format(setting, 10, true, "log.txt", "debug", 20, false);
        Console.WriteLine(text);
    }
}

Output:

worker_processes     10;
worker_rlimit_nofile    True;
error_log               logs/log.txt debug;

events
{
    worker_connections 20;
    multi_accept False;
}

Or using string interpolation from C# 6:

    return $@"worker_processes     {worker_processes};
worker_rlimit_nofile    {worker_rlimit_nofile};
error_log               logs/{error_log_file} {error_log_level};

events
{{
    worker_connections {worker_connections};
    multi_accept {multi_accept};
}}";

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