我收到此错误：“索引-1没有值。”单击组合框时 [英] I'm getting this error: "Index -1 does not have a value." when clicking a combobox

问题描述

当我点击winforms中的网格视图的组合框（下拉列表）时，我收到此错误。



索引 - 1没有价值。



请帮助我......我被困了很长时间......谷歌搜索没有运气。 :(



谢谢。

I''m getting this error when i click on the combobox (dropdown) the grid view in the winforms.

Index -1 does not have a value.

Please help me in this... I''m Stuck for a long time... No luck in googling. :(

Thanks.

推荐答案

当没有选择任何项目时，返回的索引值SelectedIndex属性为-1



在事件处理程序的顶部使用它之前检查它：

When no item is selected, the index value that is returned by the SelectedIndex property is -1

At the top of your event handler check it before you use it:

ComboBox cb = sender as ComboBox;
if (cb != null && cb.SelectedIndex >= 0)
   {
   ...
   }

嗯，我们确实需要看一些代码来帮助解决这个问题，但下面是一个快速演示：

Hi,

Umm we really do need to see some code to help on this but a quick demo below:

namespace WindowsFormsApplication160
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
   MessageBox.Show("index = "+comboBox1.SelectedIndex.ToString()+"\nvalue = "+comboBox1.Text);  
        }
    }
}

如果在阅读时组合框中没有值，则返回-1。如果您有数据，请确保显示。要显示值，请使用以下内容：

This will return -1 if there is no value in the Combo box when you read it. If you have data in it make sure it is shown. To show a value use the below:

comboBox1.SelectedIndex = 1;

这将获取您输入到组合框Items值的数据列表中的第二个值。要在C＃中充分使用组合框，请参阅

http://msdn.microsoft.com/en-us/library/system.windows.forms.combobox（v = VS.90）的.aspx [ ^ ]

希望有所帮助。

格伦

That will take the second value in the list of data that you have entered to the combo box Items value. For a full use of combo boxes in C# see
http://msdn.microsoft.com/en-us/library/system.windows.forms.combobox(v=VS.90).aspx[^]
Hope that helps.
Glenn

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