.Net ramblings
# Thursday, 05 July 2007
HowTo: Invert datagrid rows and columns
this is a bit of a strange one.  I have a table and it has approx 60 columns, with only one row being shown.  I wanted a human-readable display of all the fields in the table for any given row, i.e. i didn't want the user to have to scroll several screens across just to read the data for a single row.  Vertical scrolling is obviously easier, so i wrote a Repeater implementation, which works nicely.  For a table with X columns and Y rows, the output will have X rows and Y columns.  Screenshot below shows the output of all the ServerVariables in a HTTP-request, which is a good example of a datasource that does not naturally fit the traditional 'grid' display.
<!-- ASPX usage -->
<xyz:VerticalGrid ID="vGrid" runat="server" />

// sample databinding...
this.vGrid1.DataSource = new DataView(dataSet1.Tables[0]);
this.vGrid1.DataBind();

/// <summary>
/// A Repeater control that shows the rows and columns inverted.
/// No template is required for the items.
/// The datasource must be an ADO.Net DataView
/// </summary>
[ToolboxData("<{0}:VerticalGrid runat=server></{0}:VerticalGrid>")]
public class VerticalGrid : Repeater
{
public VerticalGrid()
{
this.EnableViewState = false;
}

protected override void Render(HtmlTextWriter writer)
{
// invert the rows and cols
if (!(base.DataSource is DataView))
throw new Exception("Error: only a dataview datasource can be used");

DataView dv = base.DataSource as DataView;

// output start of table
writer.Write("\n<table class='grid'>");

// output each row
for (int i = 0; i < dv.Table.Columns.Count; i++)
{
writer.Write("\n<tr class='{0}'><th>{1}</th>", i % 2 == 1 ? "gI" : "gA", dv.Table.Columns[i].ColumnName); // output the column name in the first cell. class names gI and gA are abbreviations of gridItem gridAlternatingItem, to reduce output markup.
for (int j = 0; j < dv.Count; j++)
writer.Write("<td>{0}</td>", dv[j].Row.IsNull(i) ? "&nbsp;" : dv[j][i].ToString());
writer.Write("</tr>");
}
writer.Write("\n</table>");
}
}




Thursday, 05 July 2007 15:53:40 (GMT Daylight Time, UTC+01:00)  #    Comments [0]  Asp.Net

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