如何将以下事件转换为javascript

我很困惑该怎么办，有办法吗？

下面是我的代码。有没有可能在JavaScript中调用方法，因为我在事件中有一个名为GetTaxDetails()的方法。

protected void ddlTaxCode_SelectedIndexChanged(object sender, EventArgs e)
{
    try
    {
        decimal taxvalue = 0;
        decimal rate = 0;
        if (txtRate.Text != "")
        {
         rate = Convert.ToDecimal(txtRate.Text);
        }
        string Taxcode = ddlTaxCode.SelectedValue.ToString();
        DataSet dsTaxDetails = new DataSet();
        objTax.TXCode = Taxcode;
        dsTaxDetails = objTax.GetTaxDetails();
        txtCalcType.Text = dsTaxDetails.Tables[0].Rows[0][4].ToString();
        decimal IncludeValue = Convert.ToDecimal(dsTaxDetails.Tables[0].Rows[0][3].ToString());
        string Calculation = Session["TaxCalcType"].ToString();
        if (Calculation == "Exclude")
        {
            txtValue.Text = IncludeValue.ToString();
            if (txtCalcType.Text == "P-Perc")
            {
                taxvalue = IncludeValue * (rate / 100);
            }
            else
            {
                taxvalue = IncludeValue;
            }
            txtTaxValue.Text = taxvalue.ToString();
            txtItemRate.Text = (taxvalue + rate).ToString();
        }
        else
        {
            decimal IncludedTaxValue = (100 + IncludeValue) / 100;
            txtValue.Text = IncludedTaxValue.ToString();
            if (txtCalcType.Text == "P-Perc")
            {
                taxvalue = rate - (rate / IncludedTaxValue);
            }
            else
            {
                taxvalue = IncludeValue;
            }
            txtTaxValue.Text = taxvalue.ToString();
            txtItemRate.Text = (rate - taxvalue).ToString();
        }
    }
    catch (Exception)
    {
        Response.Redirect("Error.aspx");
    }
}