c# - 动态生成 linq

Question

I need to dynamically generate a query to access certain columns from a datatable.

 string cols="row[Id],row[UserId], row[Code]";
 var result= (from DataRow row in dt.Rows
         select cols);

but this only returns "row[Id],row[UserId], row[Code]". How can I access the values in those columns?

Answer 1

I doubt this problem can be solved elegantly with a linq-based solution. It can be solved pretty easily using a loop and by accessing the column of the DataRow using the Item property .

public IEnumerable<object[]> GetValues(IList<string> columns, DataTable dt) {
  foreach (var row in dt.Rows) {
    var rowResult = new object[columns.Count];
    for (var col = 0; col < columns.Count; col++) {
      rowResult[col] = row.Item[columns[col]];
    }
    yield return rowResult;
  }
}

Answer 2

Why not putting it in a dictionary? Dictionary<string, object> the key is the column name and the value is the value of the column.

        string[] cols = new string[] { "Id", "UserId", "Code" };
        var result = (from DataRow row in dt.Rows
                      select cols.ToDictionary(c => c, c => row[c]));