Hi nauna,
Use below code.
HTML
<asp:TextBox ID="txtdate" runat="server" Text="abc,def,efg" AutoCompleteType="Disabled" ></asp:TextBox>
<asp:Button ID="Button2" runat="server" Text="Remove" OnClick="Button2_Click" />
Code
C#
protected void Button2_Click(object sender, EventArgs e)
{
txtdate.Text = txtdate.Text.Replace(",efg", "").Replace(",def", "");
}
VB.Net
Protected Sub Button2_Click(ByVal sender As Object, ByVal e As EventArgs)
txtdate.Text = txtdate.Text.Replace(",efg", "").Replace(",def", "")
End Sub