How to fix error The process cannot access the file because it is being used by another process.

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An exception of type 'System.IO.IOException' occurred in mscorlib.dll but was not handled in user code

Additional information: The process cannot access the file because it is being used by another process.

REPLACE: 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Text;
using System.IO;

namespace WebApplication1
{
    public partial class OpenFileIssue : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string FileDirectory = "C:\\Temp\\ExcelTest\\Test.csv";
            var reader = new StreamReader(File.OpenRead(FileDirectory));
            while (!reader.EndOfStream)
            {
                var line = reader.ReadLine();
                var values = line.Split(',');
                if (values[1].Trim() != String.Empty)
                {
                    Response.Write("found something<br />");
                }
            }
            reader = new StreamReader(File.OpenRead(FileDirectory));
            while (!reader.EndOfStream)
            {
                var line = reader.ReadLine();
                var values = line.Split(',');
                if (values[1].Trim() != String.Empty)
                {
                    Response.Write("found something");
                }
            }
            reader.Close();
            string FileDirMoved = "C:\\Temp\\ExcelTest\\Moved\\Test.csv";
            File.Move(FileDirectory, FileDirMoved);
        }
    }
}

WITH:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Text;
using System.IO;

namespace WebApplication1
{
    public partial class OpenFileIssue : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string FileDirectory = "C:\\Temp\\ExcelTest\\Test.csv";
            var reader = new StreamReader(File.OpenRead(FileDirectory));
            while (!reader.EndOfStream)
            {
                var line = reader.ReadLine();
                var values = line.Split(',');
                if (values[1].Trim() != String.Empty)
                {
                    Response.Write("found something<br />");
                }
            }
            reader.Close();
            reader = new StreamReader(File.OpenRead(FileDirectory));
            while (!reader.EndOfStream)
            {
                var line = reader.ReadLine();
                var values = line.Split(',');
                if (values[1].Trim() != String.Empty)
                {
                    Response.Write("found something");
                }
            }
            reader.Close();
            string FileDirMoved = "C:\\Temp\\ExcelTest\\Moved\\Test.csv";
            File.Move(FileDirectory, FileDirMoved);
        }
    }
}