Convert Column Values in a DataTable from byte[] to String

Question

All, I have an SQL Parser and editor which I intend to integrate in my application. When I run the following query

select * from sys.sysprocesses;

one of the columns returned is a type of byte[]. This column happily gets put into a DataTable, however, when I do

bindingSource.DataSource = result.DataTable;

and attempt to display the data in a DataGridView I get the obvious ArgumentException. In this position, what in the best way to change the byte[] to a string for display in the DataTable?

I could loop through the DataTable and do some thing like

foreach(DataColumn col in dataTable.Columns)
    if (col.DataType == typeof(byte[]))
        foreach (DataRow row in dataTable.Rows)
            row[col] = Encoding.ASCII.GetString((byte[])row[col]);

But this will attempt to put a string into a byte[] column, and will not work. I could clone the DataTable then change the type,

DataTable dtCloned = dataTable.Clone();
dtCloned.Columns[0].DataType = typeof(String);
foreach (DataRow row in dataTable.Rows)
    dtCloned.ImportRow(row);

but I need a conversion step to convert the byte[] into a hex string. What is the best and preferably most efficent way to achieve what I want?

Thanks for your time.

What's the nature of the data and how would it make sense in the form of a string? — Grant Thomas
– Grant Thomas, Commented Sep 26, 2012 at 14:46
This particular column type could be transformed to hexidecimal representation. — MoonKnight
– MoonKnight, Commented Sep 26, 2012 at 14:55

MoonKnight · Accepted Answer · 2012-09-26 16:42:09Z

This how I did this in the end.

public static void PostProcessData(ref DataTable dataTable)
{
    // Convert byte[] columns.
    List<DataColumn> colCollRem = new List<DataColumn>();
    List<DataColumn> colCollAdd = new List<DataColumn>();
    foreach(DataColumn col in dataTable.Columns)
        if (col.DataType == typeof(byte[]))
            colCollRem.Add(col);

    // Remove old add new.
    foreach (DataColumn col in colCollRem)
    {
        int tmpOrd = col.Ordinal;
        string colName = String.Format("{0}(Hex)", col.ColumnName);
        DataColumn tmpCol = new DataColumn(colName, typeof(String));
        dataTable.Columns.Add(tmpCol);
        colCollAdd.Add(tmpCol);
        foreach (DataRow row in dataTable.Rows)
            row[tmpCol] = Utilities.ByteArrayToHexString((byte[])row[col]);
        dataTable.Columns.Remove(col);
        string colNameNew = colName.Replace("(Hex)", String.Empty);
        dataTable.Columns[colName].ColumnName = colNameNew;
        dataTable.Columns[colNameNew].SetOrdinal(tmpOrd);
    }
}

Using this conversion

public static string ByteArrayToHexString(byte[] p)
{
    byte b;
    char[] c = new char[p.Length * 2 + 2];
    c[0] = '0'; c[1] = 'x';
    for (int y = 0, x = 2; y < p.Length; ++y, ++x)
    {
        b = ((byte)(p[y] >> 4));
        c[x] = (char)(b > 9 ? b + 0x37 : b + 0x30);
        b = ((byte)(p[y] & 0xF));
        c[++x] = (char)(b > 9 ? b + 0x37 : b + 0x30);
    }
    return new string(c);
}

I hope this helps someone else.

Magnus · Accepted Answer · 2012-09-26 16:45:01Z

1

If you are using SQL server 2005 or above you can do the conversion in the query by using the master.sys.fn_varbintohexstr function.
Example:

select 
  spid,
  kpid,
  ....
  master.sys.fn_varbintohexstr(sid)
from 
  sys.sysprocesses;

Edit
Or you can wrap the DataTable in a class that handles the conversion like this:
(this assumes your grid is not dependent on having a DataTable as datasource)

public class Datasource : IEnumerable
{
    private DataTable _dt;

    public Datasource(DataTable dt)
    {
        _dt = dt;
    }

    public IEnumerator GetEnumerator()
    {
        foreach (DataRow row in _dt.Rows)
        {
            IDictionary<string, object> obj = new ExpandoObject();
            for (int i = 0; i < _dt.Columns.Count; i++)
            {
                var value = row[i];
                if (value is byte[])
                    value = BitConverter.ToString((byte[])value);
                obj[_dt.Columns[i].ColumnName] = value;
            }
            yield return obj;
        }
    }
}

Usage:

bindingSource.DataSource = new Datasource(result.DataTable);

edited Sep 26, 2012 at 16:45

answered Sep 26, 2012 at 15:42

Magnus

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1 Comment

MoonKnight Over a year ago

This is useful to know but I am wanting to be able to display the results of any query the user would care to write in a DataGridView.

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