Primary Key for DataTable in C#
As we know, we can create a DataTable object in C# and can map to a database table, or we can manually add the rows in C# itself as shown below. Here we are adding three rows to DataTable dt and binding this table to DataGridView control.
using System;
using System.Data;
using System.Windows.Forms;
namespace CSharpDataTableExp
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
DataTable dt = new DataTable();
dt.Columns.Add("Employee Id");
dt.Columns.Add("Employee Name");
dt.Columns.Add("Employee Salary");
dt.Rows.Add(100, "A", 1000);
dt.Rows.Add(101, "B", 2000);
dt.Rows.Add(102, "C", 3000);
dataGridView1.DataSource = dt;
}
}
}
Sometimes we may have a requirement to add auto increment & Unique column to C# DataTable like Primary & Identity column in database table. We can achieve this by using AutoIncrement, AutoIncrementSeed, AutoIncrementStep, and Unique properties of Column & PrimaryKey property of DataTable in C# as below.
using System;
using System.Data;
using System.Windows.Forms;
namespace CSharpDataTableExp
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
DataTable dt = new DataTable();
DataColumn idColumn = dt.Columns.Add();
idColumn.ColumnName = "Employee Id";
idColumn.AutoIncrement = true;
idColumn.AutoIncrementSeed = 100;
idColumn.AutoIncrementStep = 1;
idColumn.Unique = true;
dt.PrimaryKey = new DataColumn[] { idColumn };
dt.Columns.Add("Employee Name");
dt.Columns.Add("Employee Salary");
DataRow dr1 = dt.NewRow();
dr1["Employee Name"] = "A";
dr1["Employee Salary"] = 1000;
DataRow dr2 = dt.NewRow();
dr2["Employee Name"] = "B";
dr2["Employee Salary"] = 2000;
DataRow dr3 = dt.NewRow();
dr3["Employee Name"] = "C";
dr3["Employee Salary"] = 3000;
dt.Rows.Add(dr1);
dt.Rows.Add(dr2);
dt.Rows.Add(dr3);
dataGridView1.DataSource = dt;
}
}
}
Here we are making “Employee Id”
column as primary key and identity columns starting at 100 by using AutoIncrementSeed
and AutoIncrementStep columns.
