Question

我有这段代码填充我的DataGrid：

private void getData()
{
    var context = new dbStudentEntities();        
    var data = (from s in context.tblStudents
                join c in context.tblClasses
                on s.classID equals c.classID
                select new {
                        s.studentID, c.classID, s.firstName, s.middleName, 
                        s.lastName, s.age, c.className});

    dgStudents.ItemsSource = data.ToList();
}

现在我希望我的TextBox在DataGrid中填充SelectedItem。我在SelectionChanged事件中有这个代码：

dbStudentEntities context = new dbStudentEntities();
try
{
    txtFirst.Text = ((tblStudent)dgStudents.SelectedItem).firstName.ToString();
    txtMiddle.Text = ((tblStudent)dgStudents.SelectedItem).middleName.ToString();
    txtLast.Text = ((tblStudent)dgStudents.SelectedItem).lastName.ToString();
    txtAge.Text = ((tblStudent)dgStudents.SelectedItem).age.ToString();
}
catch (Exception ex)
{
    MessageBox.Show("" + ex);
}

但每次我选择一行时，都会弹出此错误：

无法投射类型的对象 '＆LT;＆GT; f__AnonymousType0 7[System.Int32,System.Int32,System.String,System.String,System.String,System.Nullable 1 [System.Int32]，System.String]' 输入'EFStudents.tblStudent'。

我该怎么办？

Answer 1

在.xaml文件中：

<DataGrid Name="dgStudents" AutoGenerateColumns="True">
</DataGrid>

要创建对象列表，可以尝试：

List<tblStudent> data = context.tblStudents.ToList();
dgStudent.ItemsSource = data;

我可能会犯一些语法错误，所以如果它不起作用，请查看编译器错误。

首先确保de数据位于数据网格中，然后您可以担心选择项目时会发生什么。

Answer 2

好的，首先，我假设您使用EntityFramework，而您的Student类看起来像是：

public class Student
{
   public int Id {get;set;}
   public string Name {get;set;} // and other names and age and so on
   public ICollection<Class> Classes {get;set;} // classes to which student attends
}

// your context

public class dbStudentEntities : DbContext
{
   public DbSet<Student> tblStudents {get;set;} // in CodeFirst this is enough to also create Classes table
}

//    then to populate DataGrid:

using(var ctx = new dbStudentEntities()) // this is your context, disposing it is important
{
   var students = ctx.Students.Include(x => x.Classes).ToList(); // Student.Classes is not virtual, so we don't have lazy loading, but making it virtual creates ugly proxy. You can read up on that
   dataGrid.ItemsSource = students;
}

你不需要那么难看的LINQ - EF可以为你做的工作。

现在DataGrid.SelectedItem将是Student类型，因此您可以使用您的强制转换。

DataGrid SelectedItem到TextBox

2 个答案: