如何將List <>值與文本框進行比較

Question

我從清單CheckProduct(int id)發票表中獲取產品ID：

int id = int.Parse(invoice_no.Text);  // passing textbox value to list
SPBusinesslogic ab = new SPBusinesslogic();
List<SPBusinesslogic> invv = new List<SPBusinesslogic>();
invv = ab.CheckProduct(id);

 if (invv.Equals(int.Parse(up_invno_txtbox.Text)))  /comparing values in list
    {
        MessageBox.Show("the product already exist");
    }
    else
    {  //add new product code
    }

我無法比較此值，如果我犯了任何錯誤，請讓我知道。

查看產品：

public List<SPBusinesslogic> CheckProduct(int id)
{
    try
    {
        SPDatalogic sp = new SPDatalogic();
        DataTable dt = new DataTable();
        dt = sp.CheckProduct(id);
        List<SPBusinesslogic> invinfo = new List<SPBusinesslogic>();
        foreach (DataRow dr in dt.Rows)
        {
            SPBusinesslogic ab = new SPBusinesslogic();
            ab.Pro_id = int.Parse(dr[0].ToString());

            invinfo.Add(ab);
        }
        return invinfo;
    }
    catch (Exception e)
    {
        throw new Exception(e.Message);
    }

Answer 1

我懷疑您想要類似的東西 ：

// TODO: Give your variables more meaningful names throughout...
int id = int.Parse(up_invno_txtbox.Text);
if (invv.Any(item => item.Id == id))
{
    ...
}
else
{
    ...
}

顯然，可以根據您的要求調整item的使用，但是這種通用模式適合於查找謂詞的現有匹配項。

Answer 2

如果您在列表中匹配的參數是id，則該參數應可用於比較檢查

(invv.Where(a=> a.id == int.Parse(up_invno_txtbox.Text)).Count() > 0) 

甚至

(invv.Where(a=> a.id == int.Parse(up_invno_txtbox.Text)).FirstOrDefault() != null)

Answer 3

if(invv.Any(o=>o.id==Convert.ToInt32(up_invno_txtbox.Text)))
{
     MessageBox.Show("the product already exist");
}
else
{
    //add new product code

}