如何进行忽略大小写搜索 (C#)

Question

I'm trying to get an a case-insensitive search to work in C#. Currently my code is:

private void txtSearch_KeyPress_1(object sender, KeyPressEventArgs e)
{
    if (e.KeyChar == (char)13)
    {
         if (!string.IsNullOrEmpty(txtSearch.Text))
         {
              var query = from o in App.Phonebook
                          where (o.PhoneNumber.Contains(txtSearch.Text) || o.Department.Contains(txtSearch.Text) || o.Name.Contains(txtSearch.Text) || o.Email.Contains(txtSearch.Text))
                          select o;
              dataGridView.DataSource = query.ToList();
         }
         else
              dataGridView.DataSource = phonebookBindingSource;
    }
}

I have tried where (o.PhoneNumber.Contains(txtSearch.Text, StringComparison.InvariantCultureIgnoreCase) , but I get the error "No overload for method 'Contains' takes 2 arguments." I don't want to do ToUpper() and ToLower() .

Any advice would be appreciated.

Answer 1

There are various approaches.

    private void txtSearch_KeyPress_1(object sender, KeyPressEventArgs e)
    {
        if (e.KeyChar == (char)13)
        {
            if (!string.IsNullOrEmpty(txtSearch.Text))
            {
                var query = from o in App.Phonebook
                            where ((o.PhoneNumber.IndexOf(txtSearch.Text, StringComparison.InvariantCultureIgnoreCase) >= 0) || (o.Department.IndexOf(txtSearch.Text, StringComparison.InvariantCultureIgnoreCase) >= 0) || (o.Name.IndexOf(txtSearch.Text, StringComparison.InvariantCultureIgnoreCase) >= 0) || (o.Email.IndexOf(txtSearch.Text, StringComparison.InvariantCultureIgnoreCase) >= 0))
                            select o;
                dataGridView.DataSource = query.ToList();
            }
            else
                dataGridView.DataSource = phonebookBindingSource;
        }
    }

Alternative you could write an extension method:

public static class MyExtensions
{
    public static bool ContainsInsensitive(this String str, string txt)
    {
        return str.IndexOf(txt, StringComparison.InvariantCultureIgnoreCase) >= 0;
    }
}

private void txtSearch_KeyPress_1(object sender, KeyPressEventArgs e)
{
    if (e.KeyChar == (char)13)
    {
        if (!string.IsNullOrEmpty(txtSearch.Text))
        {
            var query = from o in App.Phonebook
                        where (o.PhoneNumber.ContainsInsensitive(txtSearch.Text) || o.Department.ContainsInsensitive(txtSearch.Text) || o.Name.ContainsInsensitive(txtSearch.Text) || o.Email.ContainsInsensitive(txtSearch.Text))
                            select o;
            dataGridView.DataSource = query.ToList();
        }
        else
            dataGridView.DataSource = phonebookBindingSource;
    }
}