向数据网格视图添加行时，C#中的系统参数超出范围异常

我有一个代码如下：

private void svars_MouseDoubleClick(object sender, MouseEventArgs e)
        {

            userSelection user_sel = new userSelection();
            string file = svars.SelectedItem.ToString();
            DataGridViewRow row = new DataGridViewRow();

            dataGridView1.Rows.Add(row);
            row.Cells["Local_Variables"].Value = "test";
            DataGridViewCell sysvar = new DataGridViewTextBoxCell();
            sysvar.Value = file;
            row.Cells["System_Variables"] = sysvar;
        }

我得到以下错误的错误：

An unhandled exception of type 'System.ArgumentOutOfRangeException' occurred in System.Windows.Forms.dll
Additional information: Specified argument was out of the range of valid values.

当我尝试调试时，我发现了那一行。索引为-1。我不知道该怎么修。有人能帮忙吗。

谢谢。

dataGridView1.Columns.Add("Local_Variables", "Local Variables");
dataGridView1.Columns.Add("System_Variables", "Local Variables");