如何格式化字符串ffmpeg参数将参数传递给文本框？

Question

我创建了此表格：

我想使用变量ffmpegarguments将参数从文本框传递到ffmpeg类参数。问题在于，在FFMPEG类中，我正在使用这些变量：

文件名和Framerate，因此如何使用文件名和FRAMETER变量将从文本框的输入格式化为FFMPEG参数？

在FFMPEG类中：

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Drawing;
using System.IO;
using System.IO.Pipes;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Capture_Screen
{
    internal class FFmpeg_Capture
    {
        public string workingDirectory;
        public string outputDirectory;
        public string ffmpegArguments;

        private Process process;

        public FFmpeg_Capture()
        {
            
        }

        public void Start(string FileName, int Framerate)
        {
            process = new Process();
            process.StartInfo.FileName = outputDirectory; // Change the directory where ffmpeg.exe is.  
            process.EnableRaisingEvents = false;
            process.StartInfo.WorkingDirectory = workingDirectory; // The output directory  
            process.StartInfo.Arguments = @"-y -f gdigrab -framerate " + Framerate +
                " -i desktop -preset ultrafast -pix_fmt yuv420p " + FileName;
            process.StartInfo.UseShellExecute = false;
            process.StartInfo.RedirectStandardInput = true; //Redirect stdin
            process.StartInfo.CreateNoWindow = true;
            process.Start();
        }

        public void Stop()
        {
            byte[] qKey = Encoding.GetEncoding("gbk").GetBytes("q"); //Get encoding of 'q' key
            process.StandardInput.BaseStream.Write(qKey, 0, 1); //Write 'q' key to stdin of FFmpeg sub-processs
            process.StandardInput.BaseStream.Flush(); //Flush stdin (just in case).
            process.Close();
            process.Dispose();
        }
    }
}