C＃随机化DataTable行

Question

I have a Data Table I'm using as the data source for a repeater and would like to have the results show in a random order each time it's called.

I've been able to do this while retrieving the data but wish to cache the result set before it's bound.

Is the any was to shuffle or randomise the rows of a data table before binding to the repeater?

CODE:

        TreeProvider tp = new TreeProvider();
    DataSet ds = new DataSet();
    string sKey = "KEY";
    using (CachedSection<DataSet> cs = new CachedSection<DataSet>(ref ds, 5, true, null, sKey))
    {
      if (cs.LoadData)
      {
        ds = tp.SelectNodes("", "URL", "", true, "DOCTYPE", "", "NewID()", -1, true, 5);
        cs.Data = ds;
      }
    }
    if (!DataHelper.DataSourceIsEmpty(ds))
    {
      rprItems.DataSource = ds.Tables[0].DefaultView;
      rprItems.DataBind();
    }

Any guidance is appreciated.

Answer 1

I ended up taking a copy of the table, adding a field and assigning a random number to each row then ordering by that row.

        DataTable dt = ds.Tables[0].Copy();
        if (!dt.Columns.Contains("SortBy"))
          dt.Columns.Add("SortBy", typeof (Int32));

        foreach (DataColumn col in dt.Columns)
          col.ReadOnly = false;

        Random rnd = new Random();
        foreach (DataRow row in dt.Rows)
        {
          row["SortBy"] = rnd.Next(1, 100);
        }
        DataView dv = dt.DefaultView;
        dv.Sort = "SortBy";
        DataTable sortedDT = dv.ToTable();

        rprItems.DataSource = sortedDT;
        rprItems.DataBind();

Answer 2

You could try something like this, I know it's not pretty but:

DataTable newTable = new DataTable();
newTable.TableName = "<NewTableName>";
//Make a new Random generator
Random rnd = new Random();
while (<new table length> != <old table length>)
{
    //We'll use this to make sure we don't have a duplicate row
    bool rowFound = false;
    //index generation
    int index = rnd.Next(0, <max number of rows in old data>);
    //use the index on the old table to get the random data, then put it into the new table.
    foreach (DataRow row in newTable.Rows)
    {
        if (oldTable.Rows[index] == row)
        {
            //Oops, there's duplicate data already in the new table. We don't want this.
            rowFound = true;
            break;
        }
    }
    if (!rowFound)
    {
        //add the row to newTable
        newTable.Rows.Add(oldTable.Rows[index];
    }
}

You'll have to use your own tables, names, and lengths of course, but this should be ok to use. If there's a lot of data, this could take a while. It's the best I can come up with, and it's untested. I'm curious to know if it works.

Answer 3

You could try:

        DataTable dt = new DataTable();
        dt.Columns.Add("Name");
        dt.Columns.Add("Sort");
        dt.Rows.Add("TEST");
        dt.Rows.Add("TEST1");
        dt.Rows.Add("TEST2");

        var rnd = new Random(DateTime.Now.Millisecond);
        foreach (DataRow row in dt.Rows)
        {
            row["Sort"] = rnd.Next(dt.Rows.Count);
        }


        var dv = new DataView(dt);
        dv.Sort = "Sort";
        foreach (DataRowView row in dv)
        {
            Console.WriteLine(row[0]);
        }

If your datatable is not too big it should do it.