使用LINQ从数据集中选择列 [英] select column from dataset using LINQ

问题描述

我绝对不是linq查询，请对此查询提供帮助， 数据集包含字段:

I am absolutely new to linq query, please help with this query, dataset has fields:

名称值Client_owner.

Name Value Client_owner.

如果要name == "searchtext"

DataTable results = (from d in ((DataSet)_MyDataset).Tables["Records"].AsEnumerable()
                     orderby d.Field<string>("Name") ascending
                     where d["Name"].ToString().ToLower().Contains(ProjectName.ToLower())
                     select d??).CopyToDataTable();

推荐答案

var query = (from d in _MyDataset.Tables["Records"].AsEnumerable()
                                 where d.Field<String>("Name").Equals("searchText", StringComparison.CurrentCultureIgnoreCase)
                                 select d).OrderBy(x => x.Field<String>("Name"));

if (query.Count() != 0) { DataTable result = query.CopyToDataTable(); }

如果_MyDataSet是一个DataSet对象，则在您的示例中不需要额外的转换.

if _MyDataSet is a DataSet object then the extra cast is not needed in your example.

然后创建扩展方法以创建过滤的数据表:

then create an extension method to create a filtered data table:

public static class DataTableExtensions
{
    public static DataTable ReturnColumn(this DataTable dataTable, ICollection<String> fieldNames)
    {
        if (fieldNames.Count > 0)
        {
            for (int i = 0; i < dataTable.Columns.Count; i++)
            {
                DataColumn col = dataTable.Columns[i];
                if (!fieldNames.Contains(col.ColumnName))
                {
                    dataTable.Columns.Remove(col);
                    i--;
                }
            }
        }

        return dataTable;
    }
}

然后您可以像这样过滤数据表:

you can then filter your datatable like so:

results.ReturnColumn(new List<String> { "Value" });

这将返回仅包含值"列的数据表

which will return a data table with only the column "Value"

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