Dynamic string interpolation

问题

Can anyone help me with this?

Required Output: "Todo job for admin"

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine(ReplaceMacro("{job.Name} job for admin", new Job { Id = 1, Name = "Todo", Description="Nothing" }));
        Console.ReadLine();
    }

    static string ReplaceMacro(string value, Job job)
    {
        return value; //Output should be "Todo job for admin"
    }
}

class Job
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
}

回答1:

Two suggestions:

DataBinder.Eval

string ReplaceMacro(string value, Job job)
{
    return Regex.Replace(value, @"{(?<exp>[^}]+)}", match => {
        return (System.Web.UI.DataBinder.Eval(new { Job = job }, match.Groups["exp"].Value) ?? "").ToString();
    });
}

Linq.Expression

Use the Dynamic Query class provided in the MSDN LINQSamples:

string ReplaceMacro(string value, Job job)
{
    return Regex.Replace(value, @"{(?<exp>[^}]+)}", match => {
        var p = Expression.Parameter(typeof(Job), "job");
        var e = System.Linq.Dynamic.DynamicExpression.ParseLambda(new[] { p }, null, match.Groups["exp"].Value);
        return (e.Compile().DynamicInvoke(job) ?? "").ToString();
    });
}

In my opinion, the Linq.Expression is more powerful, so if you trust the input string, you can do more interesting things, i.e.:

value = "{job.Name.ToUpper()} job for admin"
return = "TODO job for admin"

回答2:

You can't use string interpolation this way. But you can still use the pre-C#6 way to do it using string.Format:

static void Main(string[] args)
{
    Console.WriteLine(ReplaceMacro("{0} job for admin", new Job { Id = 1, Name = "Todo", Description = "Nothing" }));
    Console.ReadLine();
}

static string ReplaceMacro(string value, Job job)
{
    return string.Format(value, job.Name);
}

回答3:

You need named string format replacement. See Phil Haack's post from years ago: http://haacked.com/archive/2009/01/04/fun-with-named-formats-string-parsing-and-edge-cases.aspx/

回答4:

Answer from @ThePerplexedOne is better, but if you really need to avoid string interpolation, so

static string ReplaceMacro(string value, Job job)
{
    return value?.Replace("{job.Name}", job.Name); //Output should be "Todo job for admin"
}

回答5:

You should change your function to:

static string ReplaceMacro(Job obj, Func<dynamic, string> function)
{
    return function(obj);
}

And call it:

Console.WriteLine(
    ReplaceMacro(
        new Job { Id = 1, Name = "Todo", Description = "Nothing" },
        x => $"{x.Name} job for admin"));

回答6:

This generic solution Extend the answer provided by @Dan
It can be used for any typed object.

install System.Linq.Dynamic

     Install-Package System.Linq.Dynamic -Version 1.0.7 

    string ReplaceMacro(string value, object @object)
    {
        return Regex.Replace(value, @"{(.+?)}", 
        match => {
            var p = Expression.Parameter(@object.GetType(), @object.GetType().Name);                
            var e = System.Linq.Dynamic.DynamicExpression.ParseLambda(new[] { p }, null, match.Groups[1].Value);
            return (e.Compile().DynamicInvoke(@object) ?? "").ToString();
        });
    }

See a working demo for a Customer type

回答7:

Not exactly but with bit tweek, I have created generic interpolation which support fields / property only.

public static string Interpolate(this string template, params Expression<Func<object, string>>[] values)
        {
            string result = template;
            values.ToList().ForEach(x =>
            {
                MemberExpression member = x.Body as MemberExpression;
                string oldValue = $"{{{member.Member.Name}}}";
                string newValue = x.Compile().Invoke(null).ToString();
                result = result.Replace(oldValue, newValue);
            }

                );
            return result;
        }

Test case

 string jobStr = "{Name} job for admin";
        var d = new { Id = 1, Name = "Todo", Description = "Nothing" };
        var result = jobStr.Interpolate(x => d.Name);

Another

            string sourceString = "I wanted abc as {abc} and {dateTime} and {now}";
        var abc = "abcIsABC";
        var dateTime = DateTime.Now.Ticks.ToString();
        var now = DateTime.Now.ToString();
        string result = sourceString.Interpolate(x => abc, x => dateTime, x => now);

回答8:

Wrap the string in a function...

var f = x => $"Hi {x}";

f("Mum!");

//... Hi Mum!

回答9:

I really don't understand the point of your ReplaceMacro method...

But here's how it should work:

class Program
{
    static void Main(string[] args)
    {
        var job = new Job { Id = 1, Name = "Todo", Description = "Nothing" };
        Console.WriteLine($"{job.Name} job for admin");
        Console.ReadLine();
    }
}

But if you really want the dynamic feel to it, your ReplaceMacro method should just take one parameter, which is the job:

static string ReplaceMacro(Job job)
{
    return $"{job.Name} job for admin.";
}

And use it like:

var job = new Job { Id = 1, Name = "Todo", Description = "Nothing" };
Console.WriteLine(ReplaceMacro(job));

Or something to that effect.

来源：https://stackoverflow.com/questions/39874172/dynamic-string-interpolation

标签

string-interpolation