Question

我在布局中声明了一个DataGridView（名为dataGridView1）。我想要获得的单元格值是单元格中组合框选择的结果。基于这两个链接：MSDN和SO Post，我的代码如下所示：

private void Submit_Click(object sender, EventArgs e)
{
//output data to ResultsText richtextbox to check it
        foreach (DataGridViewRow row in dataGridView1.Rows)
        {

            foreach (DataGridViewCell cell in row.Cells)
            {
                ResultsText.Text +="\n"+ cell.Value.ToString();// getting null reference exception here

            }
        }
}

我的DataGridView代码实现：

 private void PopulateDataGridView()
    {
        dataGridView1.AutoGenerateColumns = false;
        DataTable dt = new DataTable();
        dt.Columns.Add("LoadCaseCol");

        DataGridViewComboBoxColumn lc = new DataGridViewComboBoxColumn();
        lc.DataSource = new List<string>() { "opt1", "opt2", "opt3", "opt4" };
        lc.HeaderText = "Select Load Cases";
        //lc.DataPropertyName = "Money";

        //DataGridViewTextBoxColumn name = new DataGridViewTextBoxColumn();
        //name.HeaderText = "Name";
        //name.DataPropertyName = "Name";

        dataGridView1.DataSource = dt;
        //dataGridView1.Columns.AddRange(name, money);
        dataGridView1.Columns.AddRange(lc);
    }

Answer 1

要避免使用NullReferenceException：

ResultsText.Text +="\n"+ (cell.Value == null ? "NULL" : cell.Value.ToString());

而不是

ResultsText.Text +="\n"+ cell.Value.ToString();

（假设这是问题）。

<强>已更新

由于代码初始化组合框列，可能会出现此问题。请尝试设置DataPropertyName：

private void PopulateDataGridView()
    {
        dataGridView1.AutoGenerateColumns = false;
        DataTable dt = new DataTable();
        dt.Columns.Add("LoadCaseCol");

        DataGridViewComboBoxColumn lc = new DataGridViewComboBoxColumn();
        lc.DataSource = new List<string>() { "opt1", "opt2", "opt3", "opt4" };
        lc.HeaderText = "Select Load Cases";
        lc.DataPropertyName = "LoadCaseCol";

        dataGridView1.DataSource = dt;
        dataGridView1.Columns.AddRange(lc);
    }

Answer 2

当您致电NullReferenceException时cell.Value null为ToString()，您将获得Convert.ToString()。

您可以使用null来专门检查var sb = new StringBuilder(); foreach (DataGridViewRow row in dataGridView1.Rows) { foreach (DataGridViewCell cell in row.Cells) { sb.AppendLine(Convert.ToString(cell.Value)); } } ResultsText.Text = sb.ToString();并将其转换为空字符串（防止抛出异常）：

{{1}}

从DataGridView单元格中的ComboBox访问数据

2 个答案: