Winform C# Error provider is not clearing itself despite the SetErrorProvider was appended with empty string

Question

The error provider i set for the username is not clearing itself properly. What i understand from my research is that if the SetErrorProvider was appended with an empty string, the error will be cleared itself. However, this does not work in my case. I am using Winform C# and here is my example code.

    private void usernamet_Validating(object sender, CancelEventArgs e)
    {
        ErrorProvider errorProvider = new ErrorProvider();
        if (!Regex.IsMatch(usernamet.Text, @"^[a-zA-Z0-9]*$"))
        {
            e.Cancel = true;
            errorProvider.SetError(usernamet, "Username cannot contain special characters.");
        }
        else
        {
            e.Cancel = false;
            errorProvider.Clear();
            errorProvider.SetError(usernamet, "");
            errorProvider.SetError(usernamet, null);
            errorProvider.SetError(usernamet, string.Empty);
        }
    }

i have set 4 breakpoints for each example solution i retrieved from my research, however the error is not clearing itself as shown in the pictures.

Breakpoint 1

Breakpoint 2

Breakpoint 3

Breakpoint 4

Error is not clearing itself