Design advise needed on editing and filtering a datagridview

Question

I have a design question that involves DataGridView and DataTable, bound by a BindingSource in a WinForms application. The DataTable is populated by a sql server table.

Answer 1

The filter shouldn't affect the loop. For example, in the following code I set the DataGridView.DataSource from a DataTable that has an applied filter and loop through the table, printing values:

DataTable dt = new DataTable();

dt.Columns.Add("Name", typeof(string));
dt.Columns.Add("Quantity", typeof(int));

dt.Rows.Add("Foo", 1);
dt.Rows.Add("Bar", 2);
dt.Rows.Add("Baz", 3);

string filterField = "Name";
string filterText = "B";
dt.DefaultView.RowFilter = string.Format("[{0}] LIKE '%{1}%'", filterField, filterText);

this.dataGridView1.DataSource = dt;

foreach (DataRow row in dt.Rows)
{
    Console.WriteLine("{0}", row.ItemArray[0]);
}

With the filter, the DataGridView displays only select entries. But looping through the DataTable rows still prints every entry.

Therefore, when handling binding such as a BindingSource, after the DataGridView is already sourced, you might change your filter like so to have a dynamic searching option:

private void textBox1_TextChanged(object sender, EventArgs e)
{
    BindingSource bs = this.dataGridView1.DataSource as BindingSource;
    DataTable dt = bs.DataSource as DataTable;
    dt.DefaultView.RowFilter = string.Format("[{0}] LIKE '{1}%'", "Name", this.textBox1.Text);
}

Answer 2

I just found an even better way to filter the DataGridViewfrom a question (yes it was a question) posted by mj82:

Filtering DataGridView without changing datasource

This was the most helpful part of the question.

DataTable dt = new DataTable();
BindingSource bs = new BindingSource();

private void Form1_Load(object sender, EventArgs e)
{
    dt.Columns.Add("id", typeof(int));
    dt.Columns.Add("country", typeof(string));

    dt.Rows.Add(new object[] { 1, "Belgium" });
    dt.Rows.Add(new object[] { 2, "France" });
    dt.Rows.Add(new object[] { 3, "Germany" });
    dt.Rows.Add(new object[] { 4, "Spain" });
    dt.Rows.Add(new object[] { 5, "Swiss" });
    dt.Rows.Add(new object[] { 6, "United Kingdom" });

    bs.DataSource = dt;
    dataGridView1.DataSource = bs;
}

private void textBox1_TextChanged(object sender, EventArgs e)
{
    MessageBox.Show("DataSource type BEFORE = " + dataGridView1.DataSource.GetType().ToString());

    bs.Filter = string.Format("country LIKE '%{0}%'", textBox1.Text);

    MessageBox.Show("DataSource type AFTER = " + dataGridView1.DataSource.GetType().ToString());
}