EF6没有内置的Like方法，可以使用以下自定义方法代替生成

/// <summary>
/// 应用全局关键字搜索（多字段OR连接的模糊搜索）
/// </summary>
private IQueryable<TEntity> ApplyGlobalKeywordSearch(IQueryable<TEntity> query, string keyword, List<string> propertyNames)
{
    if (string.IsNullOrEmpty(keyword) || propertyNames == null || !propertyNames.Any())
        return query;

    ParameterExpression parameter = Expression.Parameter(typeof(TEntity), "x");
    Expression combinedExpression = null;

    // 通配符包裹
    string likePattern = "%" + keyword + "%";
    ConstantExpression likePatternExpression = Expression.Constant(likePattern, typeof(string));

    foreach (string propertyName in propertyNames)
    {
        PropertyInfo property = typeof(TEntity).GetProperty(propertyName,
            BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);

        if (property == null || property.PropertyType != typeof(string))
            continue;

        MemberExpression propertyAccess = Expression.Property(parameter, property);

        // EntityFunctions.Like(x.Property, "%keyword%")
        MethodInfo likeMethod = typeof(DbFunctions).GetMethod("Like", new[] { typeof(string), typeof(string) });

        var likeExpression = Expression.Call(
            likeMethod,
            propertyAccess,
            likePatternExpression
        );

        if (combinedExpression == null)
        {
            combinedExpression = likeExpression;
        }
        else
        {
            combinedExpression = Expression.OrElse(combinedExpression, likeExpression);
        }
    }

    if (combinedExpression == null)
        return query;

    var lambda = Expression.Lambda<Func<TEntity, bool>>(combinedExpression, parameter);
    return query.Where(lambda);
}

可生成SQL语句中的 Like % keyword %