C#Winform之comboBox使用注意事项

2020-09-08 07:40:20 | CSharp | 1k+ Reads

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要说comboBox，你要用的最多的两个属性应该是DisplayMember和ValueMember。

可今天呢，为了整这个两个属性，弄了好几次发现是“”，想来想去，才发现是SelectedIndex_Changed被触发了，而引发的错误。

举个例子：

using (var myContext = new MyDbContext())
{
    var SolutionTable = myContext.MySolutions.Where(x => x.DefenceId == DefenceId1).OrderByDescending(x => x.Rank);
    //如果存在解法
    if (SolutionTable.Count() != 0)
    {
        cbxSolution1.DataSource = SolutionTable.ToList();
        //初始化Id将触发一次
        cbxSolution1.ValueMember = "Id";
        //初始化Name将触发一次    
        cbxSolution1.DisplayMember = "Name";
        //初始化SelectedIndex将触发一次，即使你不特意选中0，也会触发SelectedIndex_Changed
        cbxSolution1.SelectedIndex = 0;
        cbxSolution1.Enabled = true;
        //触发一次
        cbxSolution1_SelectedIndexChanged(sender, e);
    }
}

解决方案：

//先取消一下事件
cbxSolution1.SelectedIndexChanged -= cbxSolution1_SelectedIndexChanged;
//之后再加上去
cbxSolution1.SelectedIndexChanged += cbxSolution1_SelectedIndexChanged;

另外需要提醒的是：

cbxSolution1.DataSource = SolutionTable.ToList();

这里一定要ToList();

因为这里涉及到本地化的事情，在using里面的数据库上下文查询是会被释放掉的，不会保存，ToList()是一个最基本的本地化操作。

参考来源：

[1] Data binding directly to a store query (DbSet, DbQuery, DbSqlQuery) is not supported.

[2] C# Winform comboBox的常用一些属性和用法

[3] How to add items to Combobox from Entity Framework?  - Stack Overflow

[4] C#中comboBox控制他的SelectedIndexChanged事件何时触发问题？？？在线等待！！！！！

[5] C#调用ComboBox控件的SelectedIndexChanged事件

This article was last edited at 2020-09-08 07:45:11