Demonstrating the use of DataRow classes

(Excerpt from the C # function manual, metallurgical industry Press)

Using System;
Using System.Collections.Generic;
Using System.Text;
Using System.Data;

Namespace ConsoleApplication1
{
Class Program
{
static void Main (string[] args)
{
DataTable Testdt = new DataTable ("Student");
DataColumn Testdc;
TESTDC = new DataColumn ();
Testdc.datatype = Type.GetType ("System.Int32");
Testdc.columnname = "ID";
TESTDT.COLUMNS.ADD (TESTDC);

TESTDC = new DataColumn ();
Testdc.datatype = Type.GetType ("System.String");
Testdc.columnname = "Name";
TESTDT.COLUMNS.ADD (TESTDC);

TESTDC = new DataColumn ();
Testdc.datatype = Type.GetType ("System.String");
Testdc.columnname = "School";
TESTDT.COLUMNS.ADD (TESTDC);

DataRow TESTDR = Testdt.newrow ();
testdr["ID"] = 1;
testdr["Name" = "Rose";
testdr["School"] = "scut";
TESTDT.ROWS.ADD (TESTDR);

TESTDR = Testdt.newrow ();
testdr["ID"] = 2;
testdr["Name"] = "Coke";
testdr["School"] = "SCNU";
TESTDT.ROWS.ADD (TESTDR);

TESTDR = Testdt.newrow ();
testdr["ID"] = 3;
testdr["Name" = "Tom";
testdr["School"] = "scut";
TESTDT.ROWS.ADD (TESTDR);

Console.WriteLine ("Information of the current table:");
Doprint (TESTDT);

Console.WriteLine ("Add one line of information:");
TESTDR = Testdt.newrow ();
testdr["ID"] = 4;
testdr["Name" = "Cat";
testdr["School"] = "ZSU";
TESTDT.ROWS.ADD (TESTDR);
Console.WriteLine ("Add new row status: {0}", testdr.rowstate);
Doprint (TESTDT);

Console.WriteLine ("Perform acceptchanges operation on newly added rows ...");
Testdr.acceptchanges ();
Console.WriteLine ("Perform acceptchanges operation the state of the row: {0}", testdr.rowstate);
Doprint (TESTDT);

Console.WriteLine ("Add another line of information:");
TESTDR = Testdt.newrow ();
testdr["ID"] = 5;
testdr["Name" = "Jim";
testdr["School"] = "ZSU";
TESTDT.ROWS.ADD (TESTDR);
Console.WriteLine ("Add row status: {0}", testdr.rowstate);
Doprint (TESTDT);

Console.WriteLine ("Perform rejectchanges operation on newly added rows ...");
Testdr.rejectchanges ();
Console.WriteLine ("Perform rejectchanges operation the state of the row: {0}", testdr.rowstate);
Doprint (TESTDT);

Console.WriteLine ("Start editing ...");
foreach (DataRow Dr in Testdt.rows)
{
Dr. BeginEdit ();
DR[0] = (int) dr[0] + 10;
Dr. EndEdit ();
}
Console.WriteLine ("Edit over!");
Doprint (TESTDT);

Console.WriteLine ("Set error message:");
String errstr = "This is a wrong ID number!";
TESTDR = Testdt.rows[0];
Testdr.setcolumnerror (Testdt.columns[0], errstr);

foreach (DataRow dre in Testdt.rows)
{
Datacolumn[] DcA;
if (Dre. HasErrors)//To determine whether a row has errors
{
DcA = dre.    Getcolumnsinerror (); Gets an array of columns that contain errors
for (int i = 0; i < dca.length; i++)
{
Console.WriteLine ("Column name with error message: + dca[i]." ColumnName);
}
Console.WriteLine ("Eliminate all errors in this row.");
Dre.    Clearerrors (); Use the Clearerrors method to clear the error of the row
}
}
Console.WriteLine ();
TESTDR = testdt.rows[3];
Testdr.delete (); To delete a Datrow object using the Dete method
Testdr.acceptchanges ();
Console.WriteLine ("Delete last line!");
Doprint (TESTDT);

DataTable TESTDTC = new DataTable ("Class");
TESTDC = new DataColumn ();
Testdc.datatype = Type.GetType ("System.Int32");
Testdc.columnname = "CID";
TESTDTC.COLUMNS.ADD (TESTDC);

TESTDC = new DataColumn ();
Testdc.datatype = Type.GetType ("System.String");
Testdc.columnname = "Grade";
TESTDTC.COLUMNS.ADD (TESTDC);

String[] Pstr = {"ID"};
String[] CStr = {"CID"};
DataRelation DR = new DataRelation ("EQ", "Student", "class", Pstr, CStr, true);
foreach (DataRelation drn in testdt.childrelations)
{
foreach (DataRow Dr in Testdt.rows)
{
Datarow[] DrA = Dr. GetChildRows (DRN);
for (int i = 0; i < dra.length; i++)
{
foreach (DataColumn dc in Testdt.columns)
{
Console.WriteLine (DRA[I][DC]);
}
}
}
}
TESTDR = Testdt.rows[0]; Console.WriteLine ("First column has null value?" + testdr.isnull ("ID"));
Console.ReadLine ();
}

private static void Doprint (DataTable TEMPDT)
{
Console.WriteLine ("{0} table data:", tempdt.tablename);
foreach (DataColumn dc in Tempdt.columns)
Console.Write (DC. ColumnName + "");
Console.WriteLine ();
foreach (DataRow Dr in Tempdt.rows)
{
foreach (DataColumn dc in Tempdt.columns)
{
Console.Write (DR[DC] + "");
}
Console.WriteLine ();
}
Console.WriteLine ("------------------------------/n");
}
}
}

*****************************************************************
The results of the implementation are as follows:

Information for the current table:
Student: {0} table data:
ID Name School

1 Rose scut

2 Coke SCNU

3 Tom Scut

------------------------------

Add one line of information:
Add a new row status: Added
Student: {0} table data:
ID Name School

1 Rose scut

2 Coke SCNU

3 Tom Scut

4 Cat ZSU

------------------------------

Perform a acceptchanges operation on the newly added row ...
Perform acceptchanges operation the status of the row: unchanged
Student: {0} table data:
ID Name School

1 Rose scut

2 Coke SCNU

3 Tom Scut

4 Cat ZSU

------------------------------

Add another line of information:
Add the status of a row: Added
Student: {0} table data:
ID Name School

1 Rose scut

2 Coke SCNU

3 Tom Scut

4 Cat ZSU

5 Jim ZSU

------------------------------

Perform a rejectchanges operation on the newly added row ...
Perform rejectchanges operation the status of the row: Detached
Student: {0} table data:
ID Name School

1 Rose scut

2 Coke SCNU

3 Tom Scut

4 Cat ZSU

------------------------------

Start editing ...
Edit over!
Student: {0} table data:
ID Name School

One Rose scut

Coke SCNU

Tom Scut

Cat ZSU

------------------------------

Set error message:
Column name with error message: ID
Resolves all errors in the row.

Delete the last line!
Student: {0} table data:
ID Name School

One Rose scut

Coke SCNU

Tom Scut

------------------------------

Does the first column have a null value? False