I am completely new to the C# development world and I am working on a small application which will allow a user to add basic employee details to a employee table. I can get the code to add a row to the table but the question I asked myself is "What would happen if the user were to add a record which already exists?" Answer, it would simply add another row and so I could end up with duplicated records, how could I go about preventing this using a try/catch block?

The columns I have are EmployeeID (Unique and PK), FirstName, Surname and JobTitle.

The code I have so far is:

System.Data.SqlClient.SqlConnection connection;
System.Data.SqlClient.SqlDataAdapter adapter;
DataSet DSTestingDataSet;

private void Form1_Load(object sender, EventArgs e)

        {

            connection = new System.Data.SqlClient.SqlConnection();
            DSTestingDataSet = new DataSet();
            connection.ConnectionString = "Data Source=.\\SQLEXPRESS; etc etc";

            connection.Open();
            string sql = "SELECT * FROM Employee";
            adapter = new System.Data.SqlClient.SqlDataAdapter(sql, connection);
            adapter.Fill(DSTestingDataSet, "Employee");
            connection.Close();

        }

 private void button1_Click(object sender, EventArgs e)
        {

            System.Data.SqlClient.SqlCommandBuilder builder;
            builder = new System.Data.SqlClient.SqlCommandBuilder(adapter);

            DataTable dTable = DSTestingDataSet.Tables["Employee"];
            DataRow dRow = DSTestingDataSet.Tables["Employee"].NewRow();
            
            dRow["FirstName"] = textBox1.Text;
            dRow["Surname"] = textBox2.Text;
            dRow["JobTitle"] = textBox3.Text;

            DSTestingDataSet.Tables["Employee"].Rows.Add(dRow);

            adapter.Update(DSTestingDataSet, "Employee");

A try/catch block would only help if there is a unique index on the table that prevents duplicates.
A different solution is to first test to are if the record exists before insertion.

A try/catch block would only help if there is a unique index on the table that prevents duplicates.
A different solution is to first test to are if the record exists before insertion.

As I am a neewbie to C#, could you kindly suggest how I would do this.

you could do an INSERT statement with a WHERE clause to prevent a new row being added to a table where the same records already exits.

would be something like (but dont take my word for it)

INSERT INTO Employee AS E (Name, Age, DOB) VALUES (value1, value1, value3) WHERE E.Name != value1 AND E.Age != value2 AND E.DOB != value3;

or you could do a int recordCount = select COUNT(*) from Employee WHERE the table values match the values entered. If the value of recordCount is 0 then do the insert (as above but without the where clause in it)

Do some research on it though to make sure.

hope this helps

Those are great options, ChrisHunter!

IF NOT EXISTS (SELECT * FROM dbo.tableName WHERE PrimaryKey = @PrimaryKey)
INSERT INTO dbo.tableName(list of columns)
VALUES (list of values)