manipulate control inside a gridview

Explain your qustion in more detail.

When you want to change the text of TextBox?

Hi, try this 

  protected void gvDetail_RowCommand(object sender, GridViewCommandEventArgs e)
        {
            if (e.CommandName == "ViewDetail")
            {
                int index = Convert.ToInt32(e.CommandArgument);
                Label lblId = gvDetail.Rows[index].FindControl("lblId") as Label;

                Response.Redirect("ProductDetails2.aspx?pdid=" + lblId.Text);
            }
        }

or if you want to chang load time do this

 protected void gvCurrencyType_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.DataRow)
            {
                LinkButton lnkStatus = e.Row.FindControl("lnkStatus") as LinkButton;
                if (lnkStatus.Text == "Enable")
                {
                    lnkStatus.CssClass = "lnkEnb";
                    lnkStatus.ForeColor = Color.Green;
                    e.Row.ForeColor = Color.Black;
                }
                else
                {
                    lnkStatus.CssClass = "lnkDis";
                    lnkStatus.ForeColor = Color.Red;
                    e.Row.ForeColor = Color.Black;
                }
            }
        }