primary keys

[chronics]

When i use the code below to add a datarelation to 2 tables named 'Category' and 'Product' and then try to find a row within the tables using the find method shown below I get the error 'Table doesnt have a Primary Key'.


DataRelation catAndProdDataRelation = new DataRelation("CategoryAndProductDataRelation", ds.Tables["Category"].Columns[0]
, ds.Tables["Product"].Columns[3], true);

ds.Relations.Add(catAndProdDataRelation);


DataRow cdr = ds.Tables["Category"].Rows.Find(id);

I have also tried adding the primary keys explicitly with
ds.Tables["Category"].Constraints.Add("PK_ColumnID", ds.Tables["Category"].Columns[0], true);
ds.Tables["Product"].Constraints.Add("PK_ProductID", ds.Tables["Product"].Columns[0], true);

I get the error constraint matches constraint 1 already in collection


I thought the datarelation created the primary keys and the constraint matches error seems to indicate that.
Any help much appreciated

 

[Aptitude]

You need to add the primary keys before adding the data releation.

My sample code follows:

            // Create the dataset
            DataSet ds = new DataSet();

            // Add the two tables
            DataTable categoryTable = ds.Tables.Add("Category");
            DataTable productTable = ds.Tables.Add("Product");

            // Set up the columns
            categoryTable.Columns.Add("id", typeof(int));
            categoryTable.Columns.Add("text", typeof(string));
            productTable.Columns.Add("id", typeof(int));
            productTable.Columns.Add("text", typeof(string));
            productTable.Columns.Add("dummy", typeof(string));
            productTable.Columns.Add("categoryId", typeof(int));

            // Add some data
            categoryTable.Rows.Add(1, "Category 1");
            categoryTable.Rows.Add(2, "Category 2");
            productTable.Rows.Add(1, "1st Protuct of Category 1", "", 1);
            productTable.Rows.Add(2, "2nd Protuct of Category 1", "", 1);
            productTable.Rows.Add(3, "1st Protuct of Category 2", "", 2);

            // Add primary Keys
            ds.Tables["Category"].Constraints.Add("PK_ColumnID", ds.Tables["Category"].Columns[0], true);
            ds.Tables["Product"].Constraints.Add("PK_ProductID", ds.Tables["Product"].Columns[0], true);

            // Add the relationship
            DataRelation catAndProdDataRelation = 
                new DataRelation("CategoryAndProductDataRelation", 
                ds.Tables["Category"].Columns[0], 
                ds.Tables["Product"].Columns[3], 
                true);
            ds.Relations.Add(catAndProdDataRelation);            

            // Run the find
            int id = 1;
            DataRow cdr = ds.Tables["Category"].Rows.Find(id);

            // Display the result
            textBox1.Text = cdr["text"].ToString();

 

[chronics]

thanks aptitude putting the primary key declaration before the relationship declaration solved the problem