在将记录插入数据库“对象引用未设置为对象实例"中时，错误仍然存​​在. [英] error persisting while inserting a record in database"object reference not set to an instance of an object"

问题描述

        DialogResult dh = MessageBox.Show("DO YOU WANT TO INSERT ?", "CONFIRM YOUR INSERT", System.Windows.Forms.MessageBoxButtons.YesNo);
        if (dh != DialogResult.No)
        {
            SqlCommand cmd = new SqlCommand("exec insertcatego @description,@quality,@quantity,@priceUnit,@vat,@totalprice", con);
            cmd.Parameters.AddWithValue("@description", txtDesc.Text);
            cmd.Parameters.AddWithValue("@quality", comboBoxQuality.SelectedValue.ToString());
            cmd.Parameters.AddWithValue("@quantity", txtQant.Text);
            cmd.Parameters.AddWithValue("@priceUnit", txtpUnt.Text);
            cmd.Parameters.AddWithValue("@vat", txtVat.Text);
            cmd.Parameters.AddWithValue("@totalprice", txtTotP.Text);
            con.Close();
            con.Open();
            cmd.ExecuteNonQuery();
            frmcategory_Load(sender, e);
            MessageBox.Show("SUCCESSFULL INSERT");
        }
    }
    catch (Exception a)
    {
        MessageBox.Show(a.Message.ToString());
    }
}

推荐答案

更正了您的代码.您缺少将SqlConnection对象分配给SqlCommand命令对象.

Corrected your code. you were missing to assign the SqlConnection object to SqlCommand command object.

DialogResult dh = MessageBox.Show("DO YOU WANT TO INSERT ?", "CONFIRM YOUR INSERT", System.Windows.Forms.MessageBoxButtons.YesNo);
                if (dh != DialogResult.No)
                {
                    SqlCommand cmd = new SqlCommand("exec insertcatego @description,@quality,@quantity,@priceUnit,@vat,@totalprice", con);
                    cmd.Parameters.AddWithValue("@description", txtDesc.Text);
                    cmd.Parameters.AddWithValue("@quality", comboBoxQuality.SelectedValue.ToString());
                    cmd.Parameters.AddWithValue("@quantity", txtQant.Text);
                    cmd.Parameters.AddWithValue("@priceUnit", txtpUnt.Text);
                    cmd.Parameters.AddWithValue("@vat", txtVat.Text);
                    cmd.Parameters.AddWithValue("@totalprice", txtTotP.Text);
                    //con.Close(); 
                    cmd.Connection=new SqlConnection("your connectionString here" );//Added line of code
                    con.Open();
                    cmd.ExecuteNonQuery();
                    frmcategory_Load(sender, e);
                    MessageBox.Show("SUCCESSFULL INSERT");
                }
            }
            catch (Exception a)
            {
                MessageBox.Show(a.Message.ToString());
            }
        }

祝您好运！！！

Good luck !!!

有关异常详细信息，请参见以下链接:
对象引用未设置为对象的实例. [

Refer the following link for the exception details:
Object reference not set to an instance of an object.[^]

   DialogResult dh = MessageBox.Show("DO YOU WANT TO INSERT ?", "CONFIRM YOUR INSERT", System.Windows.Forms.MessageBoxButtons.YesNo);
        if (dh != DialogResult.No)
        {
    con.Open();
    SqlCommand cmd = new SqlCommand("INSERT INTO  category(description,quality, priceUnit,vat,totalprice) VALUES( @description, @quality, @priceUnit, @vat, @totalprice)", conn);

            cmd.Parameters.AddWithValue("@description", txtDesc.Text);
            cmd.Parameters.AddWithValue("@quality", comboBoxQuality.SelectedValue.ToString());
            cmd.Parameters.AddWithValue("@quantity", txtQant.Text);
            cmd.Parameters.AddWithValue("@priceUnit", txtpUnt.Text);
            cmd.Parameters.AddWithValue("@vat", txtVat.Text);
            cmd.Parameters.AddWithValue("@totalprice", txtTotP.Text);

            cmd.ExecuteNonQuery();
            con.Close();
    frmcategory_Load(sender, e);

            MessageBox.Show("SUCCESSFULL INSERT");
        }
    }
    catch (Exception a)
    {
        MessageBox.Show(a.Message.ToString());
    }
}

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