C# DataSet performance best practices

C# Performance optimization details

##1. Use ItemArray to implement batch assignment to DataRow

• When assigning values ​​to all fields of DataRow, using field names for column-by-column assignment is inefficient. At this time, batch field assignment should be used whenever possible. You can use the ItemArray or rows.Add method:

  / ds是数据集(DataSet)对象
  DataTable dt = ds.Tables[0];
  DataRow row = dt.NewRow();
  row.ItemArray = new object[] { value1, value2, …, valuen };
  // ds是数据集(DataSet)对象
  DataTable dt = ds.Tables[0];
  dt.Rows.Add(value1, value2, …, valuen);
  //应避免做大量连续的单列赋值，如下：
  DataTable dt = ds.Tables[0];
  DataRow row = dt.NewRow();
  row["col1"] = value1;
  row["col2"] = value2;
  …
  row["coln"] = valuen;

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2. Reasonable use of parallel computing of DataTable

• DataTable's built-in parallel computing can make full use of each CPU of the computer to optimize efficiency.

  IEnumerable<DataRow> FindRows() //查找所有数量小于0的分录
  {
      DataTable dt = ItemDataTable;
      ……
      return dt.Select(“Quantity<0”); //未使用并行计算
  }
  IEnumerable<DataRow> FindRows() //查找所有数量小于0的分录
  {
      DataTable dt = ItemDataTable;
      ……
      int index = dt.Columns.IndexOf("Quantity");
      return dt.AsEnumerable().AsParallel().Where(dr => (decimal)dr[index] < 0); //使用并行计算：
  }

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• ##According to experiments, when the DataTable Parallel computing is better than Select and loop filtering when row selection; the performance is similar when row traversal is performed.

  
  

##3. Use ImportRow to merge into DataTable with the same structure

Using the Merge method can easily achieve the merging of DataTables, but the efficiency of Merge is very poor; the example is as follows:

• DataTable[] srcTables = ... ;
  foreach(DataTable src in srcTables )
  {	
  	dest.Merge( src ) ;
  }

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ImportRow can also implement the merge operation of DataTable, and its performance is much higher than that of Merge. The code example is as follows:

• DataTable[] srcTables = ... ;
  foreach(DataTable src in srcTables )
  {
    foreach(DataRow row in src.Rows)
    {
       dest.ImportRow( row ) ;      
    }
  }

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4. To be continued

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