How to get the last item in foreach loop writing to CSV?

Question

I'm having trouble getting the last item in the loop Writing to CSV, I don't want the last item in CSV to have a , at the end.

This is the public string to write my controller to CSV

    public string WriteTsv<T>(IEnumerable<T> data)
    {
        StringBuilder output = new StringBuilder();
        PropertyDescriptorCollection props = TypeDescriptor.GetProperties(typeof(T));
        foreach (PropertyDescriptor prop in props)
        {
            output.Append(prop.DisplayName); // header
            output.Append(", \t");
        }
        output.AppendLine();
        foreach (T item in data) 
        {
            foreach (PropertyDescriptor prop in props)
            {
                output.Append(prop.Converter.ConvertToString(
                     prop.GetValue(item)));
                output.Append(", \t");
            }
            output.AppendLine();
        }
        return output.ToString();
    }

I've been stuck on this for a while now hoping anyone could help.

Answer 1

You can use String.Join to combine an IEnumerable<T> with a separator and then use AppendLine to add to the output. I used Cast<T>() to convert the IEnumerable implementation from the legacy PropertyDescriptorCollection to a modern IEnumerable<T>. (Unfortunately, a lot of C# hasn't been updated to properly support IEnumerable<T>.)

public string WriteTsv<T>(IEnumerable<T> data) {
    var output = new StringBuilder();
    var props = TypeDescriptor.GetProperties(typeof(T)).Cast<PropertyDescriptor>();
    // header
    output.AppendLine(String.Join(",", props.Select(prop => prop.DisplayName)));
    // data
    foreach (T item in data)
        output.AppendLine(String.Join(",", props.Select(prop => prop.Converter.ConvertToString(prop.GetValue(item)))));
    return output.ToString();
}