Question

我可以知道代码的问题是什么使它不能用于selectedindex＆gt; -1

此代码正常工作

if (comboBoxSubjectCodeRegister.Text != null)
{
    OleDbCommand oda1 = new OleDbCommand("select subject_abbreviation from subjectinfo where subject_code = '" + comboBoxSubjectCodeRegister.Text + "'", con);
    textBoxSubjectAbbreviationRegister.Text = Convert.ToString(oda1.ExecuteScalar());
}

else
{
    textBox1.Text = "";
}

但这不起作用

if (comboBoxSubjectCodeRegister.SelectedIndex > -1)
{
    OleDbCommand oda1 = new OleDbCommand("select subject_abbreviation from subjectinfo where subject_code = '" + comboBoxSubjectCodeRegister.Text + "'", con);
    textBoxSubjectAbbreviationRegister.Text = Convert.ToString(oda1.ExecuteScalar());
}

else
{
    textBox1.Text = "";
}

当我使用不在另一个项目中工作的代码时，它就可以了。太奇怪了，但直到现在还不确定问题是什么

Answer 1

要提供“精确”的aswer，我们需要知道如何将值绑定到ComboBox。

但是，独立于此，最好在代码中使用SelectedValue属性而不是Text：

if (comboBoxSubjectCodeRegister.SelectedIndex > -1)
{
    OleDbCommand oda1 = new OleDbCommand("select subject_abbreviation from subjectinfo where subject_code = '" + comboBoxSubjectCodeRegister.SelectedValue + "'", con);
    textBoxSubjectAbbreviationRegister.Text = Convert.ToString(oda1.ExecuteScalar());
}
else
{
    textBox1.Text = "";
}

selectedindex不在组合框中工作

1 个答案: