C# Linq to SQL：如何表达“CONVERT([...] AS INT)”？

Question

In MSSQL you can convert a string into an integer like this:

CONVERT(INT, table.column)

Is there any C# expression that Linq to SQL would translate to this?

In C# you can normally do the same by using int.Parse() , but unfortunately, trying to use int.Parse() in a Linq query results in an error:

Method 'Int32 Parse(System.String)' has no supported translation to SQL.

Is there any C# expression that Linq to SQL would translate to CONVERT(INT, ...) ?

Answer 1

C# 有Convert.ToInt32()应该做你正在寻找的。

Answer 2

Convert.ToInt32 should work. Check out this article for information on the translations.

Answer 3

for LINQ to entities, if it is simply a mismatch between your model and the DB you can overcome this using a valueconverter with EF Core.

public OnModelCreating(ModelBuilder modelBuilder) {
  modelBuilder.Entity<mymodel>()
              .Property(e => e.myModelIntColumn) // this column is a string in the db
              .HasConversion(new ValueConverter<int?, string>(m => m.HasValue ? m.ToString().Substring(0,10) : null, db => int.Parse(db ?? "0")));
}

and in my LINQ i can then use bit comparison:

MyDBSet.Where( e => (BitsWanted == 0 ||  ( e.myModelIntColumn & BitsWanted ) > 0));