How to convert string to bool and evaluate the condition? [closed]

问题

I have to convert a string to bool and evaluate the string condition. For example:

string condition = "8 > 9 || !8";

then the condition has to evaluate and return true;

if string condition = "!8"; then condition has to return true.

Suggest me how to evaluate the condition.

回答1:

Generally, if you want to evaluate C# code during runtime, you can use the .NET Compiler Platform (Roslyn) via the Microsoft.CodeAnalysis.CSharp.Scripting Nuget package.

BTW, I found this right here in stack overflow: How can I evaluate a C# expression dynamically?

here's a solution to your specific requirement, assuming the only exception to valid C# expressions is treating !8 as boolean true (specifically "!8" preceded or followed followed by any other character is forbidden).

private async Task<bool> ProcessExpression(string expression)
    {
        var processedExpression = expression.Replace("!8", "true");
        return await CSharpScript.EvaluateAsync<bool>(processedExpression);
    }

And here's some test code for the above:

Task.Run(async () =>
        {
            var expresion = "8 > 9";
            var result = await ProcessExpression(expresion);
            Console.WriteLine($"{expresion} : {result}");

            expresion = "8 < 9";
            result = await ProcessExpression(expresion);
            Console.WriteLine($"{expresion} : {result}");

            expresion = "!8";
            result = await ProcessExpression(expresion);
            Console.WriteLine($"{expresion} : {result}");

            expresion = "8 > 9 || !8";
            result = await ProcessExpression(expresion);
            Console.WriteLine($"{expresion} : {result}");

            expresion = "8 > 9 && !8";
            result = await ProcessExpression(expresion);
            Console.WriteLine($"{expresion} : {result}");
        });

The output we get is:

8 > 9 : False 8 < 9 : True !8 : True 8 > 9 || !8 : True 8 > 9 && !8 : False

please note that this solution has a performance penalty and if this is a concert than you should look for other options such as writing a dedicated parser or look for 3rd party Nuget packages.

回答2:

Try using the IValueConverter interface provided by .net

https://docs.microsoft.com/en-us/dotnet/api/system.windows.data.ivalueconverter?view=netframework-4.8

Where u define 2 methods Convert and ConvertBack Each method takes a parameter of type object and return the type object

so u can input the string and return the Boolean. As for the conversion from a string to expression you can checkout this link https://expressiontree-tutorial.net/knowledge-base/5029699/csharp-convert-string-expression-to-a-boolean-expression which have the required code cleared out.

来源：https://stackoverflow.com/questions/60261488/how-to-convert-string-to-bool-and-evaluate-the-condition

标签

.net

c#-4.0