C# Check if the data already exists

Question

I have a product record table in the database, it will save the following: ID, product code, product name, size, and price. A product can have the same size and price right? In my code, I am trying to check if the data already exists, if it already exists it won't save but if not it will save. I already tried saving a different name and size of the product but with the same price but it would say that it already exists. I am new to c# and this is in WinForms, I searched it up here but I don't understand it and it is on other language. I only know java so far. I guess this error is a logical error, but I don't know what to do.

This is what I tried so far,

cmd = new SqlCommand("select Product_Code from ProductRecord where Product_Code = @Product_Code", con);
cmd.Parameters.AddWithValue("@Product_Code", tbpcCode.Text);
DataTable dt = new DataTable();
adapt.Fill(dt);
if ( dt.Rows.Count >= 1 )
{
  MessageBox.Show("Record Already Existing");
}
else
{
  // Do save
}

I suppose Product_Code is the PK, so the data won't be inserted if it's already there — Ilyes
– Ilyes, Commented Oct 6, 2019 at 12:43
You are only searching for product code. Not for product name, price or size. If the product code alrady exist you will always get Count>0 — Chetan
– Chetan, Commented Oct 6, 2019 at 13:02
Define a UNIQUE constraint on your table. Try to insert. Catch the exception. — Serg
– Serg, Commented Oct 6, 2019 at 13:48
I just define Product_Code as UNIQUE, now the database won't allow duplicate product codes. But I don't know what to change in my if statement or in the query? should it be select * from ProductRecord where Product_Code = @Product_code ? — yoonsanha
– yoonsanha, Commented Oct 6, 2019 at 14:10

Voice Of The Rain · Accepted Answer · 2019-10-06 13:10:18Z

-1

You don't have to open connection to the database each time you create a product. In fact you can rely on the Product_Code field in your database and change it to a unique key constraint see Microsoft docs here so its going to block the insertion of duplicate products.

answered Oct 6, 2019 at 13:10

Voice Of The Rain

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