Question

我有一个DataGridView组件填充了SortableBindingList，如SQL Server SDK Microsoft.SqlServer.Management.Controls中所示。此类还用作XML序列化的根节点。

列表的成员是具有两个原始字段和一个对象字段的类型。包含原始值的列按人们期望的那样排序。但是，在对包含对象字段的列进行排序时，会抛出以下异常：

System.InvalidOperationException was unhandled
  Message=Failed to compare two elements in the array.
  Source=mscorlib
  StackTrace:
       at System.Collections.Generic.ArraySortHelper`1.Sort(T[] keys, Int32 index, Int32 length, IComparer`1 comparer)
       at System.Array.Sort[T](T[] array, Int32 index, Int32 length, IComparer`1 comparer)
       at System.Collections.Generic.List`1.Sort(Comparison`1 comparison)
       at Microsoft.SqlServer.Management.Controls.SortableBindingList`1.ApplySortCore(PropertyDescriptor prop, ListSortDirection direction)
       at System.ComponentModel.BindingList`1.System.ComponentModel.IBindingList.ApplySort(PropertyDescriptor prop, ListSortDirection direction)
       at System.Windows.Forms.BindingSource.ApplySort(PropertyDescriptor property, ListSortDirection sort)
       ...
  InnerException: System.ArgumentException
       Message=At least one object must implement IComparable.
       Source=mscorlib
       StackTrace:
            at System.Collections.Comparer.Compare(Object a, Object b)
            at Microsoft.SqlServer.Management.Controls.SortableBindingList`1.<>c__DisplayClass1.<GetComparisionDelegate>b__0(T t1, T t2)
            at System.Array.FunctorComparer`1.Compare(T x, T y)
            at System.Collections.Generic.ArraySortHelper`1.SwapIfGreaterWithItems(T[] keys, IComparer`1 comparer, Int32 a, Int32 b)
            at System.Collections.Generic.ArraySortHelper`1.QuickSort(T[] keys, Int32 left, Int32 right, IComparer`1 comparer)
            at System.Collections.Generic.ArraySortHelper`1.Sort(T[] keys, Int32 index, Int32 length, IComparer`1 comparer)

从堆栈跟踪中可以清楚地看出，被比较的对象不是IComparable - 除了它们之外。或者至少他们应该。有问题的课程如下：

using System;
using System.Xml.Serialization;

namespace myapp.xmlobjects {
    [XmlType("error_after")]
    public class ErrorAfterObject : IComparable<ErrorAfterObject> {

        [XmlAttribute("hours")]
        public int Hours { get; set; }

        [XmlAttribute("minutes")]
        public int Minutes { get; set; }

        public ErrorAfterObject() { }

        public ErrorAfterObject(int hours, int minutes) {
            this.Hours = hours;
            this.Minutes = minutes;
        }

        public override string ToString() {
            return string.Format("{0} hr {1} min", this.Hours, this.Minutes);
        }

        public int CompareTo(ErrorAfterObject other) {
            return (this.Hours*60 + this.Minutes).CompareTo(other.Hours*60 + other.Minutes);
        }
    }
}

作为一个完整性检查，我在数据绑定后添加了以下调试代码：

Console.WriteLine(myGridView.Rows[0].Cells[2].ValueType.ToString());

以我期望的方式返回myapp.xmlobjects.ErrorAfterObject。

可能有助于解决问题的三个问题：我的对象是否被输入为无法比拟的东西？是否可以准确检查正在比较的对象类型？我是否遗漏了IComparable实施中的内容？

提前致谢。

Answer 1

事实证明，IComparable和IComparable<T>不是一回事。用以下代码替换类定义：

public class ErrorAfterObject : IComparable

和CompareTo方法：

public int CompareTo(object other) {
    if(this.GetType() != other.GetType()) {
        return Comparer.Default.Compare(this, other);
    }
    return (this.Hours*60 + this.Minutes).CompareTo(
        ((ErrorAfterObject)other).Hours*60 + ((ErrorAfterObject)other).Minutes);
}

按照预期工作。

c＃SortableBindingList无法使用Object值对列进行排序

1 个答案: