将空字符串传递给EF6

Question

This code runs fine in the SQL Server Management Studio:

SELECT [PassNumber] FROM [dbo].[Customers] WHERE [PassNumber] <> 'A'

This code also works as expected:

string query = "PassNumber <> 'A'";
DbSqlQuery<Customer> data = db.Customers.SqlQuery( string.Format("select * from customers where {0}", query) );

Now it is changed to exclude empty rows and this code works fine on SSMS:

SELECT [PassNumber] FROM [Customers] WHERE [PassNumber] <> ''

But I can't find a way to correctly format the query string. I have tried all possible combinations that I thought of, but the code throws an exception: "Incorrect syntax near the keyword '<>'."

string query = "PassNumber <> '' ";
DbSqlQuery<Customer> data = db.Customers.SqlQuery( string.Format("select * from customers where {0}", query) );

NOTE: For simplicity, the check for null value has been left out of the examples in the question.

Answer 1

Why don't you use LINQ when querying in EF . Then everything might be easier:

var customerList = db.Customers.Where(c => c.PassNumber == string.Empty).ToList();

Answer 2

Have you tried to use

is null

clause on the SQL? Or is not null

Answer 3

If you insist on doing this by raw SQL you should use:

db.Customers.SqlQuery("select * from customers where PassNumber <> @p0, string.Empty);

Or

db.Customers.SqlQuery("select * from customers where LEN(PassNumber) > 0);