Question

我编写了一个代码，允许用户将数据输入程序，然后转移到excel文件。但是当我的一个文本框为空时，我不希望添加任何内容。尽管我的if else条件，仍然添加了一行。我已经调试并使用了断点，即使txt_LRU是txt_LRU，txt_LRU！= null也是如此是否有空。有人可以告诉我为什么会这样吗？

private void button_kaydet_Click(object sender, EventArgs e){

    //the text that is obtained from the text boxes and combo boxes.

    string txt_LRU = this.txtbx_LRUno.Text.ToString();
    string txt_yi = this.txtbx_yi.Text.ToString();
    string txt_td = this.cmbx_td.Text.ToString();
    string txt_toptarih = this.dtp_toplanti.Text.ToString();
    string txt_bastarih = this.dtp_bas.Text.ToString();
    string txt_teslimtarih = this.dtp_teslim.Text.ToString();
    string txt_ilgilinot = this.txtbx_ilgiliNot.Text.ToString();
    string txt_acikislem = this.txtbx_acikislem.Text.ToString();
    string txt_referedosya = this.txtbx_referedosya.Text.ToString();
    string txt_parcano = this.txtbx_parcano2.Text.ToString();

    int lru_row = 0;
    int kontrol = 0;




        //if there is non existing LRU then save the data into a new row in excel
        if (kontrol == 0)
        {
            if (txt_LRU != null || txt_LRU!="")
            {

                int x = satir_sayisi + 1;
                string satir_no = x.ToString();
                sheet1.Cells[1][satir_sayisi + 2] = satir_no;
                sheet1.Cells[2][satir_sayisi + 2] = txt_LRU;
                sheet1.Cells[3][satir_sayisi + 2] = txt_parcano;
                sheet1.Cells[4][satir_sayisi + 2] = txt_yi;
                sheet1.Cells[5][satir_sayisi + 2] = txt_acikislem;
                sheet1.Cells[7][satir_sayisi + 2] = txt_td;
                sheet1.Cells[8][satir_sayisi + 2] = txt_toptarih;
                sheet1.Cells[9][satir_sayisi + 2] = txt_bastarih;
                sheet1.Cells[10][satir_sayisi + 2] = txt_teslimtarih;
                sheet1.Cells[11][satir_sayisi + 2] = txt_ilgilinot;

            }   

            else if (txt_LRU == null || txt_LRU == "") 
                MessageBox.Show("Please add the LRU number "); 
            }


     //to save and close the excel file
    uyg.DisplayAlerts = false;
    kitap.Save();
    kitap.Close();
    uyg.DisplayAlerts = true;
    uyg.Quit();

   DialogResult dialogResult2 = MessageBox.Show("Would you like to see the excel file?", "Bilgilendirme", MessageBoxButtons.YesNo);
    if (dialogResult2 == DialogResult.Yes)
    {
        Process.Start(@"C:\\Users\\casperpc\\Desktop\\hey.xls");

    }
    else if (dialogResult2 == DialogResult.No)
    {

    }
}

Answer 1

这种情况表明，当txt_LRU不为空或非空时，您将执行操作。当txt_LRU null不等于空字符串时。此案例符合OR条件。

 if (txt_LRU != null || txt_LRU!="")
            { 
/*row added*/
     }

正确的条件是Not null AND not empty：

 if (txt_LRU != null && txt_LRU!="")
            { 
/*row added*/
     }

PS：尝试使用string.IsNullOrWhiteSpace(txt_LRU)

Answer 2

不适用于积分。

Null与零长度字符串不同。一个简单的检查可以为您提供此信息。

enter image description here

上面的代码很简单：

private void button1_Click(object sender, EventArgs e)
{
    string txt_string = this.textBox1.Text.ToString();
    if (txt_string == null)
        MessageBox.Show("Yes");
    else
        MessageBox.Show("No");
}

希望这有帮助。

Answer 3

从文本框中读取时，您正在为txt_LRU分配值。但是，如果未初始化字符串，则字符串只能为null。这就是你收到真实的原因。

请参阅this explanation。

使用C＃添加到Excel文件

3 个答案: