DataGridView AllowUserToAddRow属性不起作用 [英] DataGridView AllowUserToAddRow property doesn't work

问题描述

我有2个问题。

第一个问题是我有一个简单的实体框架项目，我有一个 DataGridView 在我的表单中，我将 AllowUserToAddRow 属性设置为 true 但仍然无法添加新行。

First problem is I have a simple project with Entity Framework, I have a DataGridView in my Form and I set its AllowUserToAddRow property to true but still I can not add new rows into it.

这里是一个屏幕截图，看看我的 DataGridView 在运行时看起来如何。

Here is a screenshot to see how my DataGridView looks like in run-time.

这里是我的代码：

DBEntities context = new DBEntities();
private void Form1_Load(object sender, EventArgs e)
{
    var q = (from i in context.myTable
             select i).ToList();
    DataGridView.DataSource = q;
}

private void btnSave_Click(object sender, EventArgs e)
{
    context.SaveChanges();
    MessageBox.Show("saved successfully");
}

第二个问题是如果我使用 BindingSource control，它允许我在 DataGridView 中插入行，但在调用 context.SaveChanges（）在我的数据库文件中没有插入。所以我认为也许它相对于这个问题， DataGridView 与 true AllowUserToAddRow 属性不允许我在 DataGridView 中插入行。

Second problem is If I use a BindingSource control, it allow me to insert rows in DataGridView but with this approach after I call context.SaveChanges() nothing insert in my database file. So I thought maybe its relative to this problem that DataGridView with true AllowUserToAddRow property doesn't let me to insert row in DataGridView.

推荐答案

您的问题是您调用 .ToList（）并实现您的查询 - 这似乎打破了完整的数据绑定。

Your problem is that you call .ToList() and materialize your query - this appears to break the full databinding.

你应该可以简单地：

DBEntities context = new DBEntities();
private void Form1_Load(object sender, EventArgs e)
{
    var q = (from i in context.myTable
             select i);
    DataGridView.DataSource = q;
}

我尝试过这个，它可以正常运行，允许新的行（你需要在你的表中有一个主键，但你应该有这个）。

I tried this and it works fine for allowing new rows (you do need to have a primary key in your table but you should have that anyway).

注意： Entity Framework 4.1中已故意破坏此行为 - Webforms数据绑定与EF Code-First Linq查询错误

Do Note: this behaviour has been intentionally broken in Entity Framework 4.1 - Webforms data binding with EF Code-First Linq query error

我说应该

I say should in my answer because I'm actually a little surprised it is this easy. I recall it not working so nicely in earlier versions of Entity Framework and I haven't used 4.0 very much.

如果上面的解决方案不起作用，你可能必须在保存之前，请自行修改此方法并自行添加新对象：

If the solution above doesn't work you may have to do this the hard way and add new objects yourself before saving:

首先介绍一个绑定源，当你保存时，做一些例子（在客户的虚构实体中） ）：

First introduce a binding source and when you save do something like (with an imaginary entity of Customer in the example):

foreach (Customer customer in bs.List)
{         
    // In my db customerId was an identity column set as primary key
    if (customer.CustomerId == 0)
        context.Customers.AddObject(customer);
}
context.SaveChanges();

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