Display DataGridView selected row cell values in TextBox in Windows Forms (WinForms) Application using C# .Net

Here I have created sample that full-fill your condition.

I hope this will you out.

C#

DataTable dt;
public Form1()
{
    InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{
    LoadData();
}

private void LoadData()
{
    dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[3] { new DataColumn("Id", typeof(int)),
                    new DataColumn("Name", typeof(string)),
                    new DataColumn("Country",typeof(string)) });
    dt.Rows.Add(1, "John Hammond", "United States");
    dt.Rows.Add(2, "Mudassar Khan", "India");
    dt.Rows.Add(3, "Suzanne Mathews", "France");
    dt.Rows.Add(4, "Robert Schidner", "Russia");
    dgvDetails.DataSource = dt;
}

private void dgvDetails_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
    txtId.Text = dgvDetails.Rows[e.RowIndex].Cells[0].Value.ToString();
    txtName.Text = dgvDetails.Rows[e.RowIndex].Cells[1].Value.ToString();
    txtCountry.Text = dgvDetails.Rows[e.RowIndex].Cells[2].Value.ToString();
    DataRow dr = dt.Rows[e.RowIndex];
    DataRow newRow = dt.NewRow();
    newRow.ItemArray = dr.ItemArray;
    dt.Rows.Remove(dr);
    dt.Rows.InsertAt(newRow, 0);
    foreach (DataGridViewRow item in dgvDetails.Rows)
    {
        dgvDetails.Rows[item.Index].Selected = false;
    }
    dgvDetails.Rows[0].Selected = true;
}

Screenshot