数组列出 <t> C＃

Question

My current code works and output is correct. I am pulling data from a data.txt file and have successfully done so to an array using TextFieldParser. Is there a way to convert my code to a List? And how so? If converting is not an option then any recommendations on where to start with the code? Basically trying to go from an array to a list collections.

public partial class EmployeeInfoGeneratorForm : Form
{
    public EmployeeInfoGeneratorForm()
    {
        InitializeComponent();
    }

    // button event handler
    private void GenerateButton_Click(object sender, EventArgs e)
    {
        string[] parts;

        if(File.Exists("..\\data.txt"))
        {
            TextFieldParser parser = new TextFieldParser("..\\data.txt");

            parser.Delimiters = new string[] { "," };
            while (true)
            {
                parts = parser.ReadFields();
                if (parts == null)
                {
                    break;
                }
                this.nameheadtxt.Text = parts[0];
                this.addressheadtxt.Text = parts[1];
                this.ageheadtxt.Text = parts[2];
                this.payheadtxt.Text = parts[3];
                this.idheadtxt.Text = parts[4];
                this.devtypeheadtxt.Text = parts[5];
                this.taxheadtxt.Text = parts[6];

                this.emp1nametxt.Text = parts[7];
                this.emp1addresstxt.Text = parts[8];
                this.emp1agetxt.Text = parts[9];
                this.emp1paytxt.Text = parts[10];
                this.emp1idtxt.Text = parts[11];
                this.emp1typetxt.Text = parts[12];
                this.emp1taxtxt.Text = parts[13];

                this.emp2nametxt.Text = parts[14];
                this.emp2addresstxt.Text = parts[15];
                this.emp2agetxt.Text = parts[16];
                this.emp2paytxt.Text = parts[17];
                this.emp2idtxt.Text = parts[18];
                this.emp2typetxt.Text = parts[19];
                this.emp2taxtxt.Text = parts[20];

                this.emp3nametxt.Text = parts[21];
                this.emp3addresstxt.Text = parts[22];
                this.emp3agetxt.Text = parts[23];
                this.emp3paytxt.Text = parts[24];
                this.emp3idtxt.Text = parts[25];
                this.emp3typetxt.Text = parts[26];
                this.emp3taxtxt.Text = parts[27];

            }

        } 
        else //Error Message for if File isn't found
        {
            lblError.Text = "File Not Found";
        }
    }
}

Answer 1

In your code example there are two arrays.

First example

parser.Delimiters = new string[] { "," };

Since parser is a TextFieldParser , I can see that Delimiters must be set to a string array. So you cannot change it.

Second example

string[] parts;
parts = parser.ReadFields();

This array accepts the result of parser.ReadFields() . The output of that function is a string array, so this code can't be changed without breaking the call.

However, you can immediately convert it to a list afterward:

var parts = parser.ReadFields().ToList();

There isn't much point to this either.

An array is just as good as a list when the size of the array/list doesn't change after it is created. Making it into a list will just add overhead.

Answer 2

There are a number of problems here. I'd be inclined to write your code like this:

public static IEnumerable<List<string>> ParseFields(string file)
{
  // Use "using" to clean up the parser.
  using (var parser = new TextFieldParser(file))
  {
    parser.Delimiters = new string[] { "," };
    // Use end-of-data, not checks for null.
    while (!parser.EndOfData)
      yield return parser.ReadFields().ToList();
  }
}

I'd refactor your code to put the UI updates in one method:

private void UpdateText(List<string> parts ) { ... }

You only do something with the last element in the sequence; all your previous edits are lost. So be explicit about that:

private void GenerateButton_Click(object sender, EventArgs e)
{
  // Use a named constant for constant strings used in several places
  const string data = "..\\data.txt";
  if(!File.Exists(data))
  {
    lblError.Text = "File Not Found";
  } else {
    var parts = ParseFields(data).LastOrDefault();
    if (parts != null) 
      UpdateText(parts);
  }
}

See how much cleaner that logic looks when you break it up into smaller parts? It's very pleasant to have methods that fit easily onto a page.

Answer 3

A direct answer to your question:

Use the List<T> constructor that takes an IEnumerable<T> parameter.

With that said, I would read Mr. Lippert's answer until you fully understand it.