在设置列的宽度时，在数据网格视图上未显示Nullreferenceexception

Question

这是我的代码

connection.Open();
        try
        {
            adpSup.SelectCommand = new SqlCommand("SELECT Supplier_Supplier AS 'Supplier', Supplier_TP AS 'Telephone', Supplier_EMail AS 'E-Mail', Supplier_Address AS 'Address' FROM Supplier", connection);
            dsSup.Clear();
            adpSup.Fill(dsSup, "tblSupplier");
            dgSupplier.DataSource = dsSup.Tables["tblSupplier"];
            dgSupplier.Columns["Telephone"].Width = 70;

            foreach (DataGridViewColumn col in dgSupplier.Columns)
            {
                col.HeaderCell.Style.Alignment = DataGridViewContentAlignment.MiddleCenter;
                col.HeaderCell.Style.Font = new Font("Arial", 12F, FontStyle.Bold, GraphicsUnit.Pixel);
            }
        }
        catch (SqlException ex)
        {
            MessageBox.Show(ex.Message, "Report", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Error);
        }
        finally
        {
            connection.Close();
        }

当我运行此代码时，它显示“System.Windows.Forms.dll中发生类型'System.NullReferenceException'的未处理异常附加信息：对象引用未设置为对象的实例。”我不知道错误是什么，请帮帮我

Answer 1

将您的Catch语句替换为：

  catch (Exception ex)
    {
        MessageBox.Show(ex.ToString(), "Report", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Error);
    }

所以你会看到发生错误的行号

Answer 2

你解决了这个问题吗？我使用DataGridView时也遇到了这个问题。最后我通过“委托”解决了这个问题。

所以我想，你的代码中的块

dgSupplier.DataSource = dsSup.Tables["tblSupplier"];
        dgSupplier.Columns["Telephone"].Width = 70;

        foreach (DataGridViewColumn col in dgSupplier.Columns)
        {
            col.HeaderCell.Style.Alignment = DataGridViewContentAlignment.MiddleCenter;
            col.HeaderCell.Style.Font = new Font("Arial", 12F, FontStyle.Bold, GraphicsUnit.Pixel);
        }

应该由代表运行。

这是我在我的代码中弄清楚的：

     //prepare data in other thread:   
            String line; 
            String[] split = null;
            DataTable table = new DataTable();
            DataRow row = null;
            StreamReader sr = new StreamReader(pCsvPath, Encoding.Default);
            line = sr.ReadLine();
            split = line.Split(',');
            foreach (String colname in split)
            {
                table.Columns.Add(colname, System.Type.GetType("System.String"));
            }
            //fill the data to the datatable
            int j = 0;
            while ((line = sr.ReadLine()) != null)
            {
                j = 0;
                row = table.NewRow();
                split = line.Split(',');
                foreach (String colname in split)
                {
                    row[j] = colname;
                    j++;
                }
                table.Rows.Add(row);
            }
            sr.Close();

            //use the delegate
            parent.showDataview(table.DefaultView);

follow是主线程中的委托代码

    private delegate void ShowDatagridView(DataView dataView);
    public void showDataview(DataView dataView)
    {
        if (this.InvokeRequired)
        {
            ShowDatagridView show = new ShowDatagridView(showDataview);
            this.Invoke(show, new object[] { dataView });
        }
        else
        {
            pmGridview.DataSource = dataView;
        }
    }

希望对你有所帮助！