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public static DataTable MergeAll(this IList<DataTable> tables, String primaryKeyColumn)
{
// Validate arguments
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");
DataTable table = new DataTable("TblUnion");
// Disable data validation during bulk loading
table.BeginLoadData();
// Merge all tables into the result table
foreach (DataTable t in tables)
table.Merge(t, false, MissingSchemaAction.Add);
// End data validation
table.EndLoadData();
// Handle duplicate primary keys (if specified)
if (primaryKeyColumn != null)
{
// Group rows by primary key column
var pkGroups = table.AsEnumerable().GroupBy(r => r[primaryKeyColumn]);
// Identify groups with duplicate keys
var dupGroups = pkGroups.Where(g => g.Count() > 1);
// Combine data from duplicate rows into the first row of each group
foreach (var grpDup in dupGroups)
{
// Use the first row and modify it to include data from other rows
DataRow firstRow = grpDup.First();
foreach (DataColumn c in table.Columns)
{
if (firstRow.IsNull(c))
{
// Find the first non-null row for the current column and copy its value
DataRow firstNotNullRow = grpDup.Skip(1).FirstOrDefault(r => !r.IsNull(c));
if (firstNotNullRow != null)
firstRow[c] = firstNotNullRow[c];
}
}
// Remove duplicate rows
var rowsToRemove = grpDup.Skip(1);
foreach (DataRow rowToRemove in rowsToRemove)
table.Rows.Remove(rowToRemove);
}
}
// Return the merged table
return table;
}
???:
var tables = new[] { tblA, tblB, tblC };
DataTable TblUnion = tables.MergeAll("c1");
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Jul 15, 2025 am 01:30 AM
STD :: Chrono? ?? ?? ??, ?? ?? ??, ?? ?? ? ?? ?? ? ?? ?? ??? ???? C?? ???? ??? ?????. 1. std :: chrono :: system_clock :: now ()? ???? ?? ??? ?? ? ??? ?? ??? ???? ?? ? ? ??? ??? ??? ???? ?? ?? ? ????. 2. std :: Chrono :: steady_clock? ???? ?? ??? ???? ?? ??? ???? duration_cast? ?? ?? ?, ? ? ?? ??? ??????. 3. ?? (time_point) ? ?? (??)? ?? ??? ? ? ??? ?? ??? ? ?? epoch (epoch)???? ???????.
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Jul 08, 2025 am 12:40 AM
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Jul 05, 2025 am 01:44 AM
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Jul 12, 2025 am 02:15 AM
C??, POD (PANDALDATA) ??? ??? ??? ?? ??? ???? C ?? ??? ??? ?????. ??? ? ?? ??? ????????. ??? ??? ?? ???? ???, ?? memcpy? ?? ?? ? ? ????. ?? ????? ?? ??? ??? ??? ? ????. ?? ?? ???? ??? ?????. ?? ? ?? ??? ??, ??? ?? ??? ?? ???, ?? ?? ?? ?? ??? ?? ? ?? ? ?? ?? ??? ?????. ?? ?? structpoint {intx; inty;}? pod???. ??? ???? ???? I/O, C ?? ???, ?? ??? ?? ?????. std :: is_pod? ?? ??? POD?? ??? ? ??? C 11 ??? std :: is_trivia? ???? ?? ????.
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Jul 09, 2025 am 02:38 AM
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