Question

根据Linq查询创建数据表我使用Ling在dataGridview上显示我的数据，并且使用linq搜索功能搜索人。它可以正常工作，但不如Datatable那样。我必须在Serch函数将其命名之前给孔名称写上名字。我想从Linq查询创建Creat DataTable，但是我不知道该怎么做。这是我的代码：

public void SerachdataEmp(string name)
{
    db = new EmployeeEntity();
    var result = (from u in db.Employee
    join d in db.Department on u.DepartmentId equals d.DepartmentId 
    where u.FirstName == name
    select new
    {                            
       FirstName = u.FirstName,
       LastName = u.LastNameName,
       DepartmentName = d.DepartmentName 
    }      
}).Tolist();
dataGridView1.DataSource = result;

我尝试过这样

(from u in db.Employee.AsEnumerable()
 join d in db.Department.AsEnumerable() on u.DepartmentId equals d.DepartmentId 
 where u.FirstName == searchEmployee

but then I don't know how to do. Thank you in advance!

Answer 1

代替使用query.ToList（）;

使用

 query.CopyToDataTable();

Answer 2

我不建议您这样做，并且我不认为您的搜索问题是不使用DataTable，但是使用这些扩展名，您可以将查询答案转换为DataTable-只需输入ToDataTable()代替ToList()。

public static class ExtensionMethods {
    // ***
    // *** IEnumerable<> Extensions
    // ***
    public static DataTable ToDataTable<T>(this IEnumerable<T> rows) {
        var dt = new DataTable();
        if (rows.Any()) {
            var rowType = typeof(T);
            var memberInfos = rowType.GetPropertiesOrFields();
            foreach (var info in memberInfos)
                dt.Columns.Add(new DataColumn(info.Name, info.GetMemberType()));

            foreach (var r in rows)
                dt.Rows.Add(memberInfos.Select(i => i.GetValue(r)).ToArray());
        }
        return dt;
    }

    // ***
    // *** MemberInfo Extensions
    // ***
    public static Type GetMemberType(this MemberInfo member) {
        switch (member) {
            case FieldInfo mfi:
                return mfi.FieldType;
            case PropertyInfo mpi:
                return mpi.PropertyType;
            case EventInfo mei:
                return mei.EventHandlerType;
            default:
                throw new ArgumentException("MemberInfo must be if type FieldInfo, PropertyInfo or EventInfo", nameof(member));
        }
    }

    public static object GetValue(this MemberInfo member, object srcObject) {
        switch (member) {
            case FieldInfo mfi:
                return mfi.GetValue(srcObject);
            case PropertyInfo mpi:
                return mpi.GetValue(srcObject);
            default:
                throw new ArgumentException("MemberInfo must be of type FieldInfo or PropertyInfo", nameof(member));
        }
    }

    // ***
    // *** Type Extensions
    // ***
    public static List<MemberInfo> GetPropertiesOrFields(this Type t, BindingFlags bf = BindingFlags.Public | BindingFlags.Instance) =>
        t.GetMembers(bf).Where(mi => mi.MemberType == MemberTypes.Field | mi.MemberType == MemberTypes.Property).ToList();
}

在C＃Windows窗体中从Linq查询创建数据表

2 个答案: