Quite often when querying databases using data from text boxes, you can run into problems dealing with a blank string and fields containing a null.<\/p>\n
A field in a table may contain a null which could also mean a blank field but you can run into problems when you are trying to query a condition on the field.<\/p>\n
This example solved the problem;<\/p>\n
var DupQuery = (from recs in db.tAXModelKitXref where (txtProdCode.Text == \"\" ? recs.ProdCode.Equals(null) : recs.ProdCode.Equals(txtProdCode.Text)) && \r\n (txtKitCode.Text == \"\" ? recs.KitCode.Equals(null) : recs.KitCode.Equals(txtKitCode.Text)) && \r\n recs.UniqueId != Unique select new { id = recs.UniqueId }).ToList();<\/pre>\nAll i’m doing in the LINQ query is checking if the textbox (a string) is blank, if it is then I pass a null to condition.<\/p>\n
If you are planning to use a null when the field is blank, then also when you are saving data to the field you need to use the followin example;<\/p>\n
Record.ProdCode = (txtProdCode.Text == \"\" ? null : txtProdCode.Text);<\/pre>\n","protected":false},"excerpt":{"rendered":"Quite often when querying databases using data from text boxes, you can run into problems dealing with a blank string and fields containing a null. A field in a table may contain a null which could also mean a blank … Continue reading