LIKE operator in LINQ

Question

Is there any way to compare strings in a C# LINQ expression similar to SQL\'s LIKE operator?

Suppose I have a string list. On this list I want to search

Answer 1

Like Extension Linq / SQL

LikeExtension Class

Tested in .NET 5

 public static class LikeExtension {

    private static string ColumnDataBase(IModel model, Expression> predicate) where TEntity : class {

        ITable table = model
            .GetRelationalModel()
            .Tables
            .First(f => f
                .EntityTypeMappings
                .First()
                .EntityType == model
                .FindEntityType(predicate
                    .Parameters
                    .First()
                .Type
            ));

        string column = (predicate.Body as MemberExpression).Member.Name;
        string columnDataBase = table.Columns.First(f => f.PropertyMappings.Count(f2 => f2.Property.Name == column) > 0).Name;

        return columnDataBase;

    }

    public static IQueryable Like(this DbContext context, Expression> predicate, string text) where TEntity : class {

        string columnDataBase = ColumnDataBase(context.Model, predicate);
        return context.Set().FromSqlRaw(context.Set().ToQueryString() + " WHERE [" + columnDataBase + "] LIKE {0}", text);

    }

    public static async Task> LikeAsync(this DbContext context, Expression> predicate, string text, CancellationToken cancellationToken) where TEntity : class {

        string columnDataBase = ColumnDataBase(context.Model, predicate);
        return await context.Set().FromSqlRaw(context.Set().ToQueryString() + " WHERE [" + columnDataBase + "] LIKE {0}", text).ToListAsync(cancellationToken);

    }

    public static async Task> LikeAsync(this IQueryable query, Expression> predicate, string text, CancellationToken cancellationToken) where TEntity : class {

        DbSet entities = query as DbSet;
        string columnDataBase = ColumnDataBase(entities.EntityType.Model, predicate);
        return await entities.FromSqlRaw(query.ToQueryString() + " WHERE [" + columnDataBase + "] LIKE {0}", text).ToListAsync(cancellationToken);

    }

    public static IQueryable Like(this IQueryable query, Expression> predicate, string text) where TEntity : class {

        DbSet entities = query as DbSet;
        string columnDataBase = ColumnDataBase(entities.EntityType.Model, predicate);
        return entities.FromSqlRaw(query.ToQueryString() + " WHERE [" + columnDataBase + "] LIKE {0}", text);

    }

}

Repository

    public async Task> LikeAsync(Expression> predicate, string text, CancellationToken cancellationToken) {

        return await context.LikeAsync(predicate, text, cancellationToken);

    }

    public IQueryable Like(Expression> predicate, string text) {

        return context.Like(predicate, text);

    }

Use

 IQueryable result = countryRepository
     .Like(k => k.Name, "%Bra[sz]il%") /*Use Sync*/
     .Where(w => w.DateRegister < DateTime.Now) /*Example*/
     .Take(10); /*Example*/

Or

 IEnumerable result = await countryRepository
     .LikeAsync(k => k.Name, "%Bra[sz]il%", cancellationToken); /*Use Async*/

Or

 IQueryable result = context.Countries
     .Like(k => k.Name, "%Bra[sz]il%")
     .Where(w => w.Name != null); /*Example*/

Or

 List result2 = await context.Countries
     .Like(k => k.Name, "%Bra[sz]il%")
     .Where(w => w.Name != null) /*Example*/
     .ToListAsync(); /*Use Async*/

Or

 IEnumerable result3 = await context.Countries
     .Where(w => w.Name != null)
     .LikeAsync(k => k.Name, "%Bra[sz]il%", cancellationToken); /*Use Async*/