C# how can I export datagridview data to a csv file

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C#

I want to export the datas in datagridview to csv file I created a class for export option then call class from the button but I'm getting the error

using System.Windows.Forms;

namespace excel2

    internal class ExportHelper
    {
        public bool Export(DataGridView dgv)
        {
            bool exported = false;

            List<string> lines = new List<string>();
            DataGridViewColumnCollection column = dgv.Columns;
            bool firstDone = false;
            StringBuilder columnLine = new StringBuilder();
            foreach(DataGridViewColumn col in column)
            {
                if(!firstDone)
                {
                    columnLine.Append(col.DataPropertyName);
                    firstDone = true;
                }
                else
                {
                    columnLine.Append("," + col.DataPropertyName);
                }
            }
            lines.Add(columnLine.ToString());

            //data lines
            foreach(DataGridViewRow row in dgv.Rows)
            {
                StringBuilder dataLine = new StringBuilder();
                firstDone = false;
                foreach(DataGridViewCell cell in row.Cells)
                {
                    if (firstDone)
                    {
                        dataLine.Append(cell.Value);
                        firstDone= true;
                    }
                    else
                    {
                        dataLine.Append(","+cell.Value);
                    }
                    lines.Add(dataLine.ToString());
                }

            }
            string file = Path.Combine(Application.StartupPath, "Excel");
            File.WriteAllLines(file,lines); //this line giving error
            System.Diagnostics.Process.Start(file);

            return exported;
        }
    }

the code I attached to button from form

private void button8_Click(object sender, EventArgs e)
{
    new ExportHelper().Export(dataGridView1);
}

the errror message : System.UnauthorizedAccessException: ''C:\Users\Yusuf\Desktop\VisualStudio\25derste25uygulamali-proje\excel2\excel2\bin\Debug\Excel' Access denied to path.'

What I have tried:

tbh I don't know what can I try, I'm sorry