Question

I have some data being shown in a DataGrid. The data comes from SQL, where a “money” type can be null. When i display this data, all is OK when i format the data in a double column format as currency. ie:

internal void FillGrid()
{

        bD = new DataTable();
        DataTable dt = EmployerQuery();  //queries the SQL DB


        bD.Columns.Add(new DataColumn("ID", typeof(int)));
        bD.Columns.Add(new DataColumn("EmployerName", typeof(string)));
        bD.Columns.Add(new DataColumn("FlatMinAmount", typeof(double)));
        bD.Columns.Add(new DataColumn("DistrictRate", typeof(double)));
        bD.Columns.Add(new DataColumn("VendorRate", typeof(double)));
        bD.Columns.Add(new DataColumn("Description", typeof(string)));
        bD.Columns.Add(new DataColumn("EmployeeCount", typeof(int)));

        foreach (DataRow sqlRow in dt.Rows)
        {
            var row = bD.NewRow();
            row["ID"] = sqlRow["ClientID"];
            row["EmployerName"] = sqlRow["OfficialName"];
            row["FlatMinAmount"] = sqlRow["FlatMinAmount"];
            row["DistrictRate"] = sqlRow["DistrictRate"];
            row["VendorRate"] = sqlRow["VendorRate"];
            row["Description"] = sqlRow["Description"];
            row["EmployeeCount"] = sqlRow["EmployeeCount"];

            bD.Rows.Add(row);

        }    

However, I then save the data as a .csv file. When i read that file back, the values for “FlatMinAmount” that were null are not allowed to be inserted into a column type double, so I cannot format the data columns as type double, since many are null.

<dg:DataGrid Name="newGrid" ItemsSource="{Binding ElementName=readGrid, Path=readGrid}" AutoGenerateColumns="False"
                 Margin="5" Height="175" Width="Auto" ColumnWidth="Auto">
        <dg:DataGrid.Columns>
            <dg:DataGridTextColumn Binding="{Binding ID}" Header="Employer ID" Width="Auto" IsReadOnly="True"/>
            <dg:DataGridTextColumn Binding="{Binding EmployerName}" Header="Employer Name" Width="Auto" IsReadOnly="True"/>
            <dg:DataGridTextColumn Binding="{Binding FlatMinAmount, StringFormat=C}" Header="FlatMinAmount" Width="Auto" IsReadOnly="True"/>
            <dg:DataGridTextColumn Binding="{Binding DistrictRate, StringFormat=C}" Header="District Rate" Width="Auto" IsReadOnly="True"/>
            <dg:DataGridTextColumn Binding="{Binding VendorRate, StringFormat=C}" Header="Vendor Rate" Width="Auto" IsReadOnly="True"/>
            <dg:DataGridTextColumn Binding="{Binding Description}" Header="Description" Width="Auto" IsReadOnly="True"/>
            <dg:DataGridTextColumn Binding="{Binding EmployeeCount}" Header="EmployeeCount" Width="*" IsReadOnly="True"/>
        </dg:DataGrid.Columns>
    </dg:DataGrid>


DataTable r = new DataTable();

        try
        {
            //string csv = string.Empty;

            //r.Columns.Add("ID", typeof(int));
            //r.Columns.Add("EmployerName", typeof(string));
            //r.Columns.Add("FlatMinAmount",typeof(double));
            //r.Columns.Add("DistrictRate", typeof(double));
            //r.Columns.Add("VendorRate", typeof(double));
            //r.Columns.Add("Description", typeof(string));
            //r.Columns.Add("EmployeeCount", typeof(int));

            r.Columns.Add("ID");
            r.Columns.Add("EmployerName");
            r.Columns.Add("FlatMinAmount");
            r.Columns.Add("DistrictRate");
            r.Columns.Add("VendorRate");
            r.Columns.Add("Description");
            r.Columns.Add("EmployeeCount");

            // Read sample data from CSV file
            using (CsvFileReader reader = new CsvFileReader(filename))
            {
                CsvRow row = new CsvRow();
                while (reader.ReadRow(row))
                {
                    //foreach (string s in row)
                    {
                        r.Rows.Add(row[0], row[1], row[2], row[3], row[4], row[5], row[6]);


                    }

                }
            }

(readGrid is then set to r in code-behind)

If they are string, then i cannot use the StringFormat=C in the binding to show $ etc. Also, it seems I cannot style a DataGridTextColumn. So, how can i display the values I read in from .csv as $xx.xx?

Answer 1

If you know the number is null, can’t you just set the value of the column to DBNull?

row["FlatMinAmount"] = DBNull.Value;

Here’s a little console app I ran to show this working:

class Program
    {
        static void Main(string[] args) {
            DataTable tbl = new DataTable();
            DataColumn col = new DataColumn("Blah", typeof(double));
            tbl.Columns.Add(col);

            DataRow row = tbl.NewRow();
            row["Blah"] = DBNull.Value;

            Console.WriteLine("Result: " + row["Blah"].ToString());
            Console.ReadKey();

        }
    }