在gridview中找到一行的单元格，然后在OnRowDataBound上执行某些操作

Question

I want to only set a single cell in a GridView row to Grey if the reader HasRows, on the OnRowDataBound event. The code snippet changes the entire column color rather than a single cell. For example: In the image I want only the cell next to "Jan" to be grey.

protected void setcolor(object sender, GridViewRowEventArgs e )
            {
                if (e.Row.RowType == DataControlRowType.DataRow)
                {               
                    if (txtShopBranch.Text == "Area1")
                        {
                            int index = e.Row.RowIndex;
                            string checkdayone = "SELECT one FROM tblregulardays WHERE  months = 'Jan'  AND shopbranch = 'Area1' AND one = '1'";
                            NpgsqlCommand findDayOne = new NpgsqlCommand (checkdayone, con);
                            con.Open();
                            NpgsqlDataReader reader = findDayOne.ExecuteReader();
                            if(reader.HasRows)
                                {
                                    e.Row.Cells[32].BackColor = System.Drawing.Color.Gray;
                                }
                            else
                                {   
                                    e.Row.Cells[32].BackColor = System.Drawing.Color.White;
                                }
                            con.Close();
                    }

                }
            }

Answer 1

You use the same static sql query for every row:

string checkdayone = @"SELECT one FROM tblregulardays 
                       WHERE  months = 'Jan'  
                          AND shopbranch = 'Area1' 
                          AND one = '1'";

so of course will always yield the same result. You have to use a parameterized query. Maybe:

string month = e.Row.Cells[31].Text.Trim();

string checkdayone = @"SELECT one FROM tblregulardays 
                       WHERE  months = @Month  
                          AND shopbranch = 'Area1' 
                          AND one = '1'";

NpgsqlCommand findDayOne = new NpgsqlCommand (checkdayone, con);
findDayOne.Parameters.AddWithValue("@Month", month);