how to read vertical grid View columns values using c#

Ok - I see.

Please remember to use the code formatting options in your posts (that's the yellow 'code' button at the top of the textarea. It adds code tags to your post. I have updated your question for you, this time.

The way that I would do this is:
1: <deleted> actually didn't need this
2: add another event handler to the gridview for DataBound which will occur after the data is bound and the other rows have been added.
3: In the event handler, sum the columns (pseudo code below) and create a gridview footer row
4: add the footer to the gridview rows.

//I took the liberty of formatting your code as well


protected void BindGridviewData()
{
    string dataId = Request.QueryString["q"];
    DataTable scoreGrid = new DataTable();

    //This will clean up connections
    using (SqlConnection conn = new SqlConnection(connString))
    {   //this will help cleanup connections
        using (SqlCommand cmd = new SqlCommand("PROC_DO_Sector_Influencer", conn))
        {
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.Add("@DO_Ticker", SqlDbType.VarChar, 50).Value = dataId;

            SqlDataAdapter da = new SqlDataAdapter(cmd);
            //Open the connection only when you need it
            conn.Open();
            da.Fill(scoreGrid );
            // ALWAYS close it
            conn.Close();
        }
    }
    gridScore.DataSource = ConvertColumnsAsRows(scoreGrid );
    gridScore.DataBind();
    gridScore.HeaderRow.Visible = false;
}

//This could prolly be better.  i haven't tested it either
protected void gridScore_DataBound(object sender, EventArgs e)
{
    // Grab the source from the grid.  It will not have the extra heading column
    DataTable dt = gridScore.DataSource as DataTable;
    if(dt==null)
        return;

    int[] footerValues = new int[dt.Columns.Count];

    //Loop through each row...
    foreach (DataRow row in dt.Rows)
    {
        //... and column
        for(int x = 0;x<dt.columns.count;x++)>
        {
            footerValues[x] += int.Parse(row[x].ToString());
        }
    }

    GridViewRow footerRow = gridScore.FooterRow;
    footerRow.Cells.Add(new TableHeaderCell
    {
        Text = @"Totals",
        ColumnSpan = 2,
        BackColor = Color.FromArgb(0xA7A6AA)
    });

    foreach (int footerValue in footerValues)
    {
        // get your image based in the value
        System.Web.UI.WebControls.Image image = GetIconFromValue(footerValue);

        TableCell cell = new TableCell();
        cell.Controls.Add(image);
        // you may need to iterate through the footer cells instead
        footerRow.Cells.Add(cell);
    }


}

protected void gridScore_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        e.Row.Cells[0].CssClass = "gridcss";
    }
}

public DataTable ConvertColumnsAsRows(DataTable dt)
{
    DataTable dtnew = new DataTable();
    //Convert all the rows to columns
    for (int i = 0; i <= dt.Rows.Count; i++)
    {
        dtnew.Columns.Add(Convert.ToString(i));
    }
    // Convert All the Columns to Rows
    for (int j = 0; j < dt.Columns.Count; j++)
    {
        var dr = dtnew.NewRow();
        dr[0] = dt.Columns[j].ToString();
        for (int k = 1; k <= dt.Rows.Count; k++)
            dr[k] = dt.Rows[k - 1][j];
        dtnew.Rows.Add(dr);
    }
    return dtnew;
}

protected void gridScore_RowCreated(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.Header)
    {
        GridViewRow headerRow = new GridViewRow(1, 0, DataControlRowType.Header, DataControlRowState.Insert);

        TableCell headerCell = new TableCell
        {
            Text = @"Score Influncers",
            ColumnSpan = 2,
            BackColor = Color.FromArgb(0xA7A6AA)
        };

        headerCell.Font.Size = 12;
        headerRow.Cells.Add(headerCell);
        gridScore.Controls[0].Controls.AddAt(0, headerRow);

    }
}