The simplest way to solve this is not to use reflection at all. You can pass the property values directly to the class constructor:

data class Member(val firstName: String, val lastName: String)

fun readCsvFileKotlin() {
    // ...
    for (line in reader) {
        val mbrProperties = line.split(",") 
        memberList.add(Member(mbrProperties[0], mbrProperties[1]))
    }
}

If you want to set properties through reflection, you need to declare them as var rather than val, so that they can be changed after the object is created. Then you can use the set method on the property object to change the property value:

data class Member(var firstName: String? = null, var lastName: String? = null)

fun readCsvFileKotlin() {
    // ...
    val prop = Member::firstName
    for (line in reader) { 
        val mbrProperties = line.split(",") 
        val member = Member()
        prop.set(member, mbrProperties[0])
        memberList.add(member)
    }
}

Check this post - https://www.baeldung.com/kotlin/csv-files - it contains a few nice references to some libraries or pure Kotlin approaches if you prefer to use those.

Applying it to your use case, maybe something like:

fun OutputStream.writeCsv(context: Context, listOfData: List<YourData>) {
    //get data create directory
   ......

    val writer = bufferedWriter()
    writer.write(""""Name", "Address", "Code"""")
    writer.newLine()
    listOfData.forEach {
        writer.write("${it.name}, ${it.address}, \"${it.code}\"")
        writer.newLine()
    }
    writer.flush()
    writer.close()
}

And then call this where you need it,

FileOutputStream("out777.cs").apply { writeCsv(listOfData) }

One thing to note here is using bufferedWriter:

FileWriter writes directly into Files and should be used only when the number of writes is less. BufferedWriter: BufferedWriter is almost similar to FileWriter but it uses internal buffer to write data into File. So if the number of write operations is more, the actual IO operations are less and performance is better.

Not tested but this might point you in a more cleaner and efficient solution. There are also some libraries specifically for this. Take a look

This can be achieved using basic Kotlin instead of an external library.

data class

data class Category(
    val id: String,
    val name: String,
)

utility function

fun <T> csvOf(
    headers: List<String>,
    data: List<T>,
    itemBuilder: (T) -> List<String>
) = buildString {
    append(headers.joinToString(",") { "\"$it\"" })
    append("\n")
    data.forEach { item ->
        append(itemBuilder(item).joinToString(",") { "\"$it\"" })
        append("\n")
    }
}

usage

fun main() {
    val firstCategory = Category(0, "Phone")
    val secondCategory = Category(1, "Laptop")
    val categories = listOf(firstCategory, secondCategory)
    val csv = csvOf(
        listOf("id", "name"),
        categories
    ) {
        listOf(it.id.toString(), it.name)
    }
    println(csv)
}