错误:对象引用未设置为对象的实例" [英] error:Object reference not set to an instance of an object"

问题描述

我使用了2个gridview，并且在后面使用了以下代码:

I used 2 gridview and I used this code behind:

protected void SAVE_bt_Click(object sender, EventArgs e)
    {
        if (Hidden_txt.Text == Convert.ToString(1))
        {
            
            for (int i = 0; i < FirstDD_gv.Rows.Count; i++)
            {
                GridViewRow row = FirstDD_gv.Rows[i];
                bool isChecked = ((CheckBox)row.FindControl("chkSelect")).Checked;

                if (isChecked)
                {

                    SqlCommand cmd = new SqlCommand();
                    cmd.Connection = new SqlConnection(Class1.CnnStr);
                    cmd.CommandText = "insert into table values(@Po_Number,@Line_No,@DelDate,@First_Sec)";
                    cmd.Connection.Open();
                    cmd.Parameters.AddWithValue("@Po_Number", PoNumber_lbl.Text);
                    cmd.Parameters.AddWithValue("@Line_No", FirstDD_gv.Rows[i].Cells[1].Text);
                    cmd.Parameters.AddWithValue("@DelDate", DeliveryDate_txt.Text);
                    cmd.Parameters.AddWithValue("@First_Sec", Hidden_txt.Text);
                    cmd.ExecuteNonQuery();

                }
            }
        }
        else
        {
           
            for (int i = 0; i < SecondDD_gv.Rows.Count; i++)
            {
                GridViewRow row = SecondDD_gv.Rows[i];
                bool isChecked = ((CheckBox)row.FindControl("chkSelect")).Checked;

                if (isChecked)
                {

                    SqlCommand cmd = new SqlCommand();
                    cmd.Connection = new SqlConnection(Class1.CnnStr);
                    cmd.CommandText = "insert into table values(@Po_Number,@Line_No,@DelDate,@First_Sec)";
                    cmd.Connection.Open();
                    cmd.Parameters.AddWithValue("@Po_Number", PoNumber_lbl.Text);
                    cmd.Parameters.AddWithValue("@Line_No", SecondDD_gv.Rows[i].Cells[1].Text);
                    cmd.Parameters.AddWithValue("@DelDate", DeliveryDate_txt.Text);
                    cmd.Parameters.AddWithValue("@First_Sec", Hidden_txt.Text);
                    cmd.ExecuteNonQuery();

                }
            }
        }


    }

取决于我的hidden_txt.text，其中仅显示了其中一个
当我使用第一个网格视图时，我没有任何问题，但是当我使用第二个网格视图时，它显示了此错误:
对象引用未设置为对象的实例"
我该怎么办?

depends on my hidden_txt.text that just shows one of them
when I used first gridview I don''t have any problem but when I used second grid view It shows me this error:
"Object reference not set to an instance of an object"
what should I do?

推荐答案

要做的第一件事是找出出现错误的那一行！在您的方法周围放置try ... catch块:

The first thing to do is to find out which line is giving the error! Put a try...catch block around your method:

protected void SAVE_bt_Click(object sender, EventArgs e)
     {
     try
         {
         if (Hidden_txt.Text == Convert.ToString(1))
             {
             ...
             }
         else
             {
             ...
             }
         }


     catch (Exception ex)
         {
         // Log or display ex.ToString() here
         }
     }

获得该信息后，您可以开始查看可能是什么问题.

When you have that info, you can start to look at what might be the problem.

您的数据源和网格应具有相同的数据类型.行数不会影响.

Your data source and grid should have same data type. The number of rows dosen''t affect.

添加以下代码:

Add the following codes:

if(!String.IsNullOrEmpty(Hidden_txt.Text))
{
   if (Hidden_txt.Text == Convert.ToString(1))
   {
      //your code here.
   }
}

希望对您有帮助！

问候，
爱德华

Hope it helps!

Regards,
Eduard

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