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数据视图。排序-不仅仅是asc/desc(需要自定义排序)

asp.net c#

bugfixr · 技术社区 · 16 年前

order by 
    case when field = 'Some Value' then 0 end
    case when field = 'Another Value' then 1 end

基本上重新定义我的排序(即,某个值在另一个值之前)。

是否有可能对DataView执行类似于排序表达式的操作?

7 回复 | 直到 16 年前

BFree 16 年前

DataView .)

你可以在原件上做这件事 DataTable 通过添加计算 DataColumn (使用 Expression

DataColumn c = myTable.Columns.Add("Sort", typeof(int));
c.Expression = "iif(field='SomeValue', 0, iif(field='AnotherValue', 1, 2))";

哪种 SomeValue 第一, AnotherValue

Robert Rossney 16 年前

public static class DataTableExtensions
{
    public static DataView ApplySort(this DataTable table, Comparison<DataRow> comparison)
    {

        DataTable clone = table.Clone();
        List<DataRow> rows = new List<DataRow>();
        foreach (DataRow row in table.Rows)
        {
            rows.Add(row);    
        }

        rows.Sort(comparison);

        foreach (DataRow row in rows)
        {
            clone.Rows.Add(row.ItemArray);
        }

        return clone.DefaultView;
    }


}

    DataTable table = new DataTable();
    table.Columns.Add("IntValue", typeof(int));
    table.Columns.Add("StringValue");

    table.Rows.Add(11, "Eleven");
    table.Rows.Add(14, "Fourteen");
    table.Rows.Add(10, "Ten");
    table.Rows.Add(12, "Twelve");
    table.Rows.Add(13, "Thirteen");

//按字符串值排序:

 DataView sorted = table.ApplySort((r, r2) =>
        {
            return ((string)r["StringValue"]).CompareTo(((string)r2["StringValue"]));
        });

11十一

13十三

//按IntValue排序:

DataView sorted = table.ApplySort((r, r2) =>
            {
                return ((int)r["IntValue"]).CompareTo(((int)r2["IntValue"]));
            });

11十一

13十三

12十二

现在,在您的Lambda中(或者您可以创建一个完整的Comparison方法),您可以执行所需的任何类型的自定义排序逻辑。记住,-1小于,0等于,1大于。

Stuart 13 年前

public class Versioning : IComparable {
    string _version;

    int _major;
    public int Major { 
        get { return (_major); } 
        set { _major = value; } 
    }

    int _minor;
    public int Minor {
        get { return (_minor); }
        set { _minor = value; }
    }

    int _beta;
    public int Beta {
        get { return (_beta); }
        set { _beta = value; }
    }

    int _alpha;
    public int Alpha {
        get { return (_alpha); }
        set { _alpha = value; }
    }

    public Versioning(string version) {
        _version = version;

        var splitVersion = SplitVersion();
        if (splitVersion.Length < 4) {
            Major = Minor = Beta = Alpha = 0;
        }

        if (!int.TryParse(splitVersion[0], out _major)) _major = 0;
        if (!int.TryParse(splitVersion[1], out _minor)) _minor = 0;
        if (!int.TryParse(splitVersion[2], out _beta)) _beta = 0;
        if (!int.TryParse(splitVersion[3], out _alpha)) _alpha = 0;
    }

    string[] SplitVersion() {
        return (_version.Split('.'));
    }

    int GetCompareTo(Versioning versioning) {
        var greater = -1;
        var equal = 0;
        var less = 1;

        if (Major > versioning.Major) return (greater);
        if (Major < versioning.Major) return (less);
        if (Minor > versioning.Minor) return (greater);
        if (Minor < versioning.Minor) return (less);
        if (Beta > versioning.Beta) return (greater);
        if (Beta < versioning.Beta) return (less);
        if (Alpha > versioning.Alpha) return (greater);
        if (Alpha < versioning.Alpha) return (less);

        return (equal);
    }

    public int CompareTo(Versioning versioning) {
        return (GetCompareTo(versioning));
    }

    public override string ToString() {
        return (_version);
    }

    public int CompareTo(object obj) {
        if (obj == null) return (1);
        return (GetCompareTo((Versioning)obj));
    }
}

当您将该列添加到表中时,不是将Version添加为字符串,而是将其添加为Versioning类:

_table.Columns.Add("Version", typeof(Versioning));
_view = new View(_table);

然后正常排序:

_view.Sort = "Version";

user53794 16 年前

select
    (case when f = 'a' then 0 else 1 end) as CustomSort
from MyTable

REA_ANDREW 16 年前

您可以使用if或switch语句来获得与select case语句类似的功能:

            if (Something == "1")
                MyView.Sort = "Field1 ASC";
            else
                MyView.Sort = "Field2 ASC";

或

            switch (MyProperty)
            {
                case 1:
                    MyView.Sort = "Field1 ASC";
                    break;
                case 2:
                    MyView.Sort = "Field2 ASC";
                    break;
                default:
                    MyView.Sort = "Field3 ASC";
                    break;
            }