How do you put { and } in a format string [duplica

问题:

This question already has answers here:

How to escape braces (curly brackets) in a format string in .NET (10 answers)

Closed 5 years ago.

I'm trying to generate some code at runtime where I put in some boiler-plate stuff and the user is allowed to enter the actual working code. My boiler-plate code looks something like this:

using System;

public class ClassName
{
    public double TheFunction(double input)
    {
        // user entered code here
    }
}

Ideally, I think I want to use string.Format to insert the user code and create a unique class name, but I get an exception on the format string unless it looks like this:

string formatString = @"
using System;

public class ClassName
{0}
    public double TheFunction(double input)
    {0}
        {2}
    {1}
{1}";

Then I call string.Format like this:

string entireClass = string.Format(formatString, "{", "}", userInput);

This is fine and I can deal with the ugliness of using {0} and {1} in the format string in place of my curly braces except that now my user input cannot use curly braces either. Is there a way to either escape the curly braces in my format string, or a good way to turn the curly braces in the user code into {0}'s and {1}'s?

BTW, I know that this kind of thing is a security problem waiting to happen, but this is a Windows Forms app that's for internal use on systems that are not connected to the net so the risk is acceptable in this situation.

回答1:

Escape them by doubling them up:

string s = String.Format("{{ hello to all }}");
Console.WriteLine(s); //prints '{ hello to all }'

From http://msdn.microsoft.com/en-us/netframework/aa569608.aspx#Question1

回答2:

"{{" and "}}"

回答3:

What I think you want is this...

string formatString = @"
using System;

public class ClassName
{{
    public double TheFunction(double input)
    {{
        {0}
    }}
}}";

string entireClass = string.Format(formatString, userInput);

回答4:

Double the braces: string.Format("{{ {0} }}", "Hello, World"); would produce { Hello, World }

回答5:

Be extra extra cautious in who has access to the application. A better solution might be to create a simple parser that only expects a few, limited, commands.