Running an R-script from C#

Question

I have the following R script and C# program that is used as an example of calling R from C#. If I run the script from within R-GUI, I see the expected output. However, if I run it from within C# as below, I get no output. I tried moving the R script inside the C# executable directory, and this doesn't work either. I tried running Visual Studio as Administrator, again no output.

Not sure what I am doing wrong:

R code:

# Gradient Boosting model with gbm
# Turn off library warning messages
suppressWarnings(library(gbm))


# gbm result for simulated data
get_gbm <- function()
{
    set.seed(123)
    a <- sample(1:10, 250, replace = T)
    b <- sample(10:20, 250, replace = T)
    flag <- ifelse(a > 5 & b > 10, "red", ifelse(a < 3, "yellow", "green"))
    df <- data.frame(a = a, b = b, flag = as.factor(flag))

    train <- df[1:200,]
    test <- df[200:250,]

    mod_gb <- gbm(flag ~ a + b,
                  data = train,
                  distribution = "multinomial",
                  shrinkage = .01,
                  n.minobsinnode = 10,
                  n.trees = 100)

    pred <- predict.gbm(object = mod_gb,
                        newdata = test,
                        n.trees = 100,
                        type = "response")

    res <- cbind(test, pred)
    return(res)
}

# need to call function to get the output
get_gbm()

C# code:

using System;
using System.Diagnostics;
using System.IO;

class Program
{
    static void Main(string[] args)
    {
        var rmainpath = @"C:\Program Files\R\R-4.0.3";
        var rpath = rmainpath +  @"\bin\Rscript.exe";

        var mainGoogleDrivePath = @"C:\Users\Administrator\Google Drive";
        //var scriptpath = mainGoogleDrivePath + @"\repos\rsource\Script.R";
        var scriptpath = mainGoogleDrivePath + @"\Projects\RFromCSharp\RFromCSharp\bin\Debug\Script.R";
        var output = RunRScript(rpath, scriptpath);

        Console.WriteLine(output); // output is empty
        Console.ReadLine();
    }

    private static string RunRScript(string rpath, string scriptpath)
    {
        try
        {
            var info = new ProcessStartInfo
            {
                FileName = rpath,
                WorkingDirectory = Path.GetDirectoryName(scriptpath),
                Arguments = scriptpath,
                RedirectStandardOutput = true,
                CreateNoWindow = true,
                UseShellExecute = false
            };

            using (var proc = new Process { StartInfo = info })
            {
                if (false == proc.Start())
                    throw new Exception("Didn't start R");

                return proc.StandardOutput.ReadToEnd();
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
        return string.Empty;
    }
}