How do I copy and paste datagridview cell values in C#

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C#

I'm developing a desktop application in c#. The copy seems to work well but on pasting clipboard values, it throws an error String must be exactly one character long at line:
string [] lines = clipboardvalues.Split(char.Parse(environment. NewLine));

How can I correct it to paste cells on datagridview.

What I have tried:

private DataGridViewCell GetStartingCell(DataGridView dgView)
{
    if (dgView.SelectedCells.Count == 0)
    {
        return null;
    }
    int rowIndex = dgView.Rows.Count - 1;
    int ColIndex = dgView.Columns.Count - 1;

    foreach (DataGridViewCell dgvcell in dgView.SelectedCells)
    {
        if (dgvcell.RowIndex < rowIndex)
        {
            rowIndex = dgvcell.RowIndex;
        }
        if (dgvcell.ColumnIndex < ColIndex)
        {
            ColIndex = dgvcell.ColumnIndex;
        }
    }
    return dgView[ColIndex, rowIndex];
}
private Dictionary<int, Dictionary<int, string>> ClipboardValues(string clipboardvalue)
{
    Dictionary<int, Dictionary<int, string>> copyValues = new Dictionary<int, Dictionary<int, string>>();
    string[] lines = clipboardvalue.Split(char.Parse(Environment.NewLine));
    for (int i = 0; i < lines.Length; i++)
    {
        copyValues[i] = new Dictionary<int, string>();
        string[] linecontent = lines[i].Split((char)Keys.Tab);
        if (linecontent.Length == 0)
        {
            copyValues[i][0] = string.Empty;
        }
        else
        {
            for (int j = 0; j < linecontent.Length; j++)
            {
                copyValues[i][j] = linecontent[j];
            }
        }
    }
    return copyValues;
}
public void PasteClipboardValue ()
{
    if (STMDataGridView.Focus())
    {
        if (STMDataGridView.SelectedCells.Count == 0)
        {
            MessageBox.Show("Please, select a cell", "Paste", MessageBoxButtons.OK, MessageBoxIcon.Warning);
            return;
        }
        DataGridViewCell StartingCell = GetStartingCell(STMDataGridView);
        Dictionary<int, Dictionary<int, string>> cbvalue = ClipboardValues(Clipboard.GetText());
        int irowindex = StartingCell.RowIndex;
        foreach (int rowkey in cbvalue.Keys)
        {
            int icolindex = StartingCell.ColumnIndex;
            foreach (int cellkey in cbvalue[rowkey].Keys)
            {
                if (icolindex <= STMDataGridView.Columns.Count - 1 && irowindex <= STMDataGridView.Rows.Count - 1)
                {
                    DataGridViewCell cell = STMDataGridView[icolindex, irowindex];
                    cell.Value = cbvalue[rowkey][cellkey].TrimStart();
                }
                icolindex += 1;
            }
            irowindex += 1;
        }
    }

}