学步园

 private void DemonstrateMergeMissingSchema()<br /> {<br /> // Create a DataSet with one table, two columns,<br /> // and three rows.<br /> DataSet dataSet = new DataSet("dataSet");<br /> DataTable table = new DataTable("Items");<br /> DataColumn idColumn = new DataColumn("id",<br /> Type.GetType("System.Int32"));<br /> idColumn.AutoIncrement=true;<br /> DataColumn itemColumn = new DataColumn("Item",<br /> Type.GetType("System.Int32"));<br /> // DataColumn array to set primary key.</p> <p> DataColumn[] keyColumn= new DataColumn[1];<br /> DataRow row;<br /> // Create variable for temporary DataSet.<br /> DataSet changeDataSet;</p> <p> // Add RowChanged event handler for the table.<br /> table.RowChanged+= new DataRowChangeEventHandler(<br /> Row_Changed);<br /> dataSet.Tables.Add(table);<br /> table.Columns.Add(idColumn);<br /> table.Columns.Add(itemColumn);</p> <p> // Set primary key column.<br /> keyColumn[0]= idColumn;<br /> table.PrimaryKey=keyColumn;</p> <p> // Add ten rows.<br /> for(int i = 0; i <10;i++)<br /> {<br /> row=table.NewRow();<br /> row["Item"]= i;<br /> table.Rows.Add(row);<br /> }</p> <p> // Accept changes.<br /> dataSet.AcceptChanges();<br /> DataGrid2.DataSource=dataSet;<br /> DataGrid2.DataBind();<br /> //PrintValues(dataSet, "Original values");</p> <p> // Change row values.<br /> table.Rows[0]["Item"]= 50;<br /> table.Rows[1]["Item"]= 111;</p> <p> // Add one row.<br /> row=table.NewRow();<br /> row["Item"]=74;<br /> table.Rows.Add(row);</p> <p> // Insert code for error checking. Set one row in error.<br /> table.Rows[1].RowError= "over 100";<br /> //PrintValues(dataSet, "Modified and New Values");<br /> // If the table has changes or errors, create a subset DataSet.<br /> if(dataSet.HasChanges(DataRowState.Modified |<br /> DataRowState.Added)& dataSet.HasErrors)<br /> {<br /> // Use GetChanges to extract subset.<br /> changeDataSet = dataSet.GetChanges(<br /> DataRowState.Modified|DataRowState.Added);<br /> //PrintValues(changeDataSet, "Subset values");</p> <p> // Insert code to reconcile errors. Reject the changes.<br /> foreach(DataTable changeTable in changeDataSet.Tables)<br /> {<br /> if (changeTable.HasErrors)<br /> {<br /> foreach(DataRow changeRow in changeTable.Rows)<br /> {<br /> //Console.WriteLine(changeRow["Item"]);<br /> if((int)changeRow["Item",<br /> DataRowVersion.Current ]> 100)<br /> {<br /> changeRow.RejectChanges();<br /> changeRow.ClearErrors();<br /> }<br /> }<br /> }<br /> }<br /> // Add a column to the changeDataSet to change the schema.<br /> changeDataSet.Tables["Items"].Columns.Add(<br /> new DataColumn("newColumn"));<br /> //PrintValues(changeDataSet, "Reconciled subset values");</p> <p> // Add values to the rows for each column.<br /> foreach(DataRow rowItem in changeDataSet.Tables["Items"].Rows)<br /> {<br /> rowItem["newColumn"] = "my new schema value";<br /> }<br /> DataGrid2.DataSource=dataSet;<br /> DataGrid2.DataBind();<br /> DataGrid3.DataSource=changeDataSet;<br /> DataGrid3.DataBind();<br /> // Merge changes back to first DataSet.<br /> dataSet.Merge(changeDataSet, false,<br /> System.Data.MissingSchemaAction.Add);<br /> }<br /> //PrintValues(dataSet, "Merged Values");<br /> DataGrid1.DataSource=dataSet;<br /> DataGrid1.DataBind();<br /> }</p> <p> private void Row_Changed(object sender, DataRowChangeEventArgs e)<br /> {<br /> Console.WriteLine("Row Changed " + e.Action.ToString()<br /> + "/table" + e.Row.ItemArray[0]);<br /> }</p> <p> private void PrintValues(DataSet dataSet, string label)<br /> {<br /> Console.WriteLine("/n" + label);<br /> foreach(DataTable table in dataSet.Tables)<br /> {<br /> Console.WriteLine("TableName: " + table.TableName);<br /> foreach(DataRow row in table.Rows)<br /> {<br /> foreach(DataColumn column in table.Columns)<br /> {<br /> Console.Write("/table " + row[column] );<br /> }<br /> Console.WriteLine();<br /> }<br /> }<br /> }</p> <p>id Item<br /> 0 50<br /> 1 111<br /> 2 2<br /> 3 3<br /> 4 4<br /> 5 5<br /> 6 6<br /> 7 7<br /> 8 8<br /> 9 9<br /> 10 74 </p> <p>id Item newColumn<br /> 0 50 my new schema value<br /> 1 1 my new schema value<br /> 10 74 my new schema value </p> <p> id Item newColumn<br /> 0 50 my new schema value<br /> 1 1 my new schema value<br /> 2 2<br /> 3 3<br /> 4 4<br /> 5 5<br /> 6 6<br /> 7 7<br /> 8 8<br /> 9 9<br /> 10 74 my new schema value<br />