Question

我有一个拥有100,000+ DataRow的数据表。哪种方法访问集合更快？有没有更快的方法来处理行集合？方法1：

var rows= dsDataSet.Tables["dtTableName"].Rows;
int rowCount = dsDataSet.Tables["dtTableName"].Rows.Count;

for (int c = 0; c < rowCount; c++)
{
    var theRow = rows[c];        
    //process the dataRow 
}

方法2：

for (int c = 0; c < dsDataSet.Tables["dtTableName"].Rows.Count; c++)
{
    var theRow = dsDataSet.Tables["dtTableName"].Rows[c];
    //process the dataRow 
}

Answer 1

值得注意的是，访问单元的最直接方式是通过DataColumn索引器;数据实际上存储在列中，而不是行中（不是：真的）。

类似于：

var table = dataSet.Tables["dtTableName"];

// HERE: fetch the DataColumn of those you need, for example:
var idCol = table.Columns["Id"];
var nameCol = table.Columns["Name"];

// now loop
foreach(DataRow row in table.Rows)
{
    var id = (int)row[idCol];
    var name = (string)row[nameCol];
    // ...
}

但是，坦率地说，如果你想获得最佳表现，我会首先说“不要使用DataSet / DataTable”。这实际上是一个非常复杂的模型，设计为各种灵活的，具有变更跟踪，规则执行等。如果你想快，我会使用POCO和类似“dapper”的东西，例如：

public class Foo {
    public int Id {get;set;}
    public string Name {get;set;}
}
...
string region = "North";
foreach(var row in conn.Query<Foo>("select * from [Foo] where Region = @region",
         new { region })) // <=== simple but correct parameterisation
{
    // TODO: do something with row.Id and row.Name, which are direct
    // properties of the Foo row returned
    var id = row.Id;
    var name = row.Name;
    // ...
}

甚至可以通过dynamic跳过该类型：

string region = "North";
foreach(var row in conn.Query("select * from [Foo] where Region = @region",
         new { region })) // ^^^ note no <Foo> here
{
    // here "row" is dynamic, but still works; not quite as direct as a
    // POCO object, though
    int id = row.Id;        // <=== note we can't use `var` here or the
    string name = row.Name; // variables would themselves be "dynamic"
    // ...
}

访问DataTable / DataRow集合的更快捷方式是什么？

1 个答案: