C# 连接两个数据表

Question

我正在尝试加入两个数据表，它们的行数相同，只有一列。 C# 中有什么奇特的方法可以做到这一点吗？结果，我需要包含两列的数据表，其中第一列的第一行紧挨第二列的第一行。

Answer 1

这是执行此操作的一种方法，所以基本上它使用.Select 的重载，它提供迭代中当前位置的索引，以查找我们当前在@987654323 中查看的table2 中的相应行@。我们为每一行从每个表中生成一个包含两个项目的对象数组。然后我们可以使用LoadDataRow 将它们放入包含两列的目标表中。

// create a target table with 2 columns
DataTable destinationTable = new DataTable();
destinationTable.Columns.Add("Col1");
destinationTable.Columns.Add("Col2");

// select all the rows from the first table, combined with the corresponding value for that row in the second table
var rowsCombined = table1
    .AsEnumerable()
    .Select((row, rowNumber) => new object[] { row[0], table2.Rows[rowNumber][0] });

foreach (var data in rowsCombined)
    destinationTable.LoadDataRow(data, true);       

Answer 2

来自 Tim Schmelter 在此链接上的 ANSWER....

public static DataTable MergeAll(this IList<DataTable> tables, String   primaryKeyColumn)
{
    if (!tables.Any())
        throw new ArgumentException("Tables must not be empty", "tables");
    if(primaryKeyColumn != null)
        foreach(DataTable t in tables)
            if(!t.Columns.Contains(primaryKeyColumn))
                throw new ArgumentException("All tables must have the specified primarykey column " + primaryKeyColumn, "primaryKeyColumn");

    if(tables.Count == 1)
        return tables[0];

    DataTable table = new DataTable("TblUnion");
    table.BeginLoadData(); // Turns off notifications, index maintenance, and constraints while loading data
    foreach (DataTable t in tables)
    {
        table.Merge(t); // same as table.Merge(t, false, MissingSchemaAction.Add);
    }
    table.EndLoadData();

    if (primaryKeyColumn != null)
    {
        // since we might have no real primary keys defined, the rows now might have repeating fields
        // so now we're going to "join" these rows ...
        var pkGroups = table.AsEnumerable()
            .GroupBy(r => r[primaryKeyColumn]);
        var dupGroups = pkGroups.Where(g => g.Count() > 1);
        foreach (var grpDup in dupGroups)
        { 
            // use first row and modify it
            DataRow firstRow = grpDup.First();
            foreach (DataColumn c in table.Columns)
            {
                if (firstRow.IsNull(c))
                {
                    DataRow firstNotNullRow =  grpDup.Skip(1).FirstOrDefault(r => !r.IsNull(c));
                    if (firstNotNullRow != null)
                        firstRow[c] = firstNotNullRow[c];
                }
            }
            // remove all but first row
            var rowsToRemove = grpDup.Skip(1);
            foreach(DataRow rowToRemove in rowsToRemove)
                table.Rows.Remove(rowToRemove);
        }
    }

    return table;
}

可以这样调用：

var tables = new[] { tblA, tblB, tblC };
DataTable TblUnion = tables.MergeAll("c1");

一些样本数据：

var tblA = new DataTable();
tblA.Columns.Add("c1", typeof(int));
tblA.Columns.Add("c2", typeof(int));
tblA.Columns.Add("c3", typeof(string));
tblA.Columns.Add("c4", typeof(char));

var tblB = new DataTable();
tblB.Columns.Add("c1", typeof(int));
tblB.Columns.Add("c5", typeof(int));
tblB.Columns.Add("c6", typeof(string));
tblB.Columns.Add("c7", typeof(char));

var tblC = new DataTable();
tblC.Columns.Add("c1", typeof(int));
tblC.Columns.Add("c8", typeof(int));
tblC.Columns.Add("c9", typeof(string));
tblC.Columns.Add("c10", typeof(char));

tblA.Rows.Add(1, 8500, "abc", 'A');
tblA.Rows.Add(2, 950, "cde", 'B');
tblA.Rows.Add(3, 150, "efg", 'C');
tblA.Rows.Add(4, 850, "ghi", 'D');
tblA.Rows.Add(5, 50, "ijk", 'E');

tblB.Rows.Add(1, 7500, "klm", 'F');
tblB.Rows.Add(2, 900, "mno", 'G');
tblB.Rows.Add(3, 150, "opq", 'H');
tblB.Rows.Add(4, 850, "qrs", 'I');
tblB.Rows.Add(5, 50, "stu", 'J');

tblC.Rows.Add(1, 7500, "uvw", 'K');
tblC.Rows.Add(2, 900, "wxy", 'L');
tblC.Rows.Add(3, 150, "yza", 'M');
tblC.Rows.Add(4, 850, "ABC", 'N');
tblC.Rows.Add(5, 50, "CDE", 'O');

mergeAll 调用后：

希望这会有所帮助...