c# - How to use textbox to search data in data grid view?

Question

Here's my current code:

private void searchTextBox_TextChanged(object sender, EventArgs e)
    {
        (dataGridView1.DataSource as DataTable).DefaultView.RowFilter = string.Format("Name='{0}'", searchTextBox.Text);

    }

However my data grid table filters everything and becomes blank whenever I type something into the textbox. Any idea why? Thank you in advance!

Answer 1

The likely reason you are seeing a blank DataGridView is due to your filter string searching for exact matches to the TextBox text.

"Name='{0}'"

Because you are updating this filter in the TextBox.TextChanged event, the first time you enter a character - no matches are found. For example, given the following grid:

╔════╦══════╗                    ╔════════╗
║ ID ║ Name ║      searchTextBox ║        ║
╠════╬══════╣                    ╚════════╝
║ 1  ║ Foo  ║
║ 2  ║ Bar  ║
║ 3  ║ Baz  ║
╚════╩══════╝

Entering Bar will give the following results:

╔════╦══════╗                    ╔════════╗
║ ID ║ Name ║      searchTextBox ║ B      ║
╠════╬══════╣                    ╚════════╝
╚════╩══════╝
╔════╦══════╗                    ╔════════╗
║ ID ║ Name ║      searchTextBox ║ Ba     ║
╠════╬══════╣                    ╚════════╝
╚════╩══════╝
╔════╦══════╗                    ╔════════╗
║ ID ║ Name ║      searchTextBox ║ Bar    ║
╠════╬══════╣                    ╚════════╝
║ 2  ║ Bar  ║
╚════╩══════╝

If this is the case, I've provided a few options below. If this is not the case, then you have a mystery.

---

1. Exact matches: consider using the following event handler instead so that the filter is only applied once you've entered the full search text:

   private void searchTextBox_Leave(object sender, EventArgs e)
   {
       if (string.IsNullOrEmpty(searchTextBox.Text))
       {
           (dataGridView1.DataSource as DataTable).DefaultView.RowFilter = string.Empty;
       }
       else
       {
           (dataGridView1.DataSource as DataTable).DefaultView.RowFilter = string.Format("Name='{0}'", searchTextBox.Text);
       }
   }
   

2. StartsWith matches: for more fluid filtering on text changes:

   private void searchTextBox_TextChanged(object sender, EventArgs e)
   {
       (dataGridView1.DataSource as DataTable).DefaultView.RowFilter = string.Format("Name LIKE '{0}%'", searchTextBox.Text);
   }
   

3. Contains matches: again, fluid filtering:

   private void searchTextBox_TextChanged(object sender, EventArgs e)
   {
       (dataGridView1.DataSource as DataTable).DefaultView.RowFilter = string.Format("Name LIKE '%{0}%'", searchTextBox.Text);
   }