CODEWITHSUNDEEP
c#datagridview
Just Rudy
Just Rudy

Reputation: 700

How to change the cell value for entire datagridview column?

I'd like for the datagridview column to check all, or check none. The code below works, but is there an easier/faster way of doing this? For setting the value for all the cells in a column?

if(searchResultsGrid.Columns["checkboxColumn"].HeaderText == "CheckAll")
{
    searchResultsGrid.Columns["checkboxColumn"].HeaderText = "UncheckAll";
    foreach (DataGridViewRow row in searchResultsGrid.Rows)
    {
        row.Cells["checkboxColumn"].Value = true;
        searchResultsGrid.UpdateCellValue(0, row.Index);
    }
}
else
{
    searchResultsGrid.Columns["checkboxColumn"].HeaderText = "CheckAll";
    foreach (DataGridViewRow row in searchResultsGrid.Rows)
    {
        row.Cells["checkboxColumn"].Value = false;
        searchResultsGrid.UpdateCellValue(0, row.Index);
    }
}

Upvotes: 2

Views: 1652

Answers (1)

OhBeWise
OhBeWise

Reputation: 5454

You could achieve this another way through some trickery. The column must be ReadOnly and the cell values Null. Clicking any cell in the column will toggle the default NullValue of the column; essentially toggling every cell.

DataGridViewCheckBoxColumn chk = new DataGridViewCheckBoxColumn(false);
chk.HeaderText = "CheckAll";
chk.Name = "checkboxColumn";
chk.ReadOnly = true;
this.dataGridView1.Columns.Add(chk);

this.dataGridView1.CellClick += DataGridView1_ToggleAll;

private void DataGridView1_ToggleAll(object sender, DataGridViewCellEventArgs e)
{
    DataGridViewCheckBoxColumn col = this.dataGridView1.Columns[e.ColumnIndex] as DataGridViewCheckBoxColumn;

    if (col?.Name == "checkboxColumn")
    {
        bool checkAll = (bool)col.DefaultCellStyle.NullValue;
        col.HeaderText = checkAll ? "CheckAll" : "UncheckAll";
        col.DefaultCellStyle.NullValue = !checkAll;
    }
}

But note: to get the checked state you'd use cell.EditedFormattedValue and not cell.Value. (Because Value of necessity would always be null for this trick to work.)

This has a creative touch to it, but you must also think about future developers. When you decide to optimize code, you must ask how it will affect maintenance. Loops are easily understood and still execute quickly. You have to weigh the worth.

Below are snippets from my findings in 100 runs each with 10,000 rows of data. These were the run times of toggling the rows:

Standard Looping

Elapsed = 00:00:00.0315538
Elapsed = 00:00:00.0107964
Elapsed = 00:00:00.0676696
Elapsed = 00:00:00.0232370
Elapsed = 00:00:00.0243285

NullValue Toggling

Elapsed = 00:00:00.0006645
Elapsed = 00:00:00.0006712
Elapsed = 00:00:00.0006804
Elapsed = 00:00:00.0007579
Elapsed = 00:00:00.0003037

Note: NullValue toggling speed was consistent despite number of rows. For small data (1000 rows), looping was 2/3rd's faster than the NullValue method.

Upvotes: 1

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