ABP报错：System.ArgumentNullException: 值不能为 null。 参数名: unitOfWork

在ABP项目中做执行SQL语句的实现时，遇到如下错误：

ERROR 2020-09-26 11:16:16,098 [7 ] oryRepositories.xxxRepository - SELECT * FROM xxx Error.
System.ArgumentNullException: 值不能为 null。
参数名: unitOfWork
在 Niue.Abp.Abp.EntityFramework.EntityFramework.Uow.UnitOfWorkExtensions.GetDbContext[TDbContext](IActiveUnitOfWork unitOfWork, Nullable1 multiTenancySide) 位置 C:\xxx\Abp.EntityFramework\EntityFramework\Uow\UnitOfWorkExtensions.cs:行号 33 在 Niue.Abp.Abp.EntityFramework.EntityFramework.Uow.UnitOfWorkDbContextProvider1.GetDbContext(Nullable1 multiTenancySide) 位置 C:\xxx\Abp.EntityFramework\EntityFramework\Uow\UnitOfWorkDbContextProvider.cs:行号 33 在 Niue.Abp.Abp.EntityFramework.EntityFramework.Uow.UnitOfWorkDbContextProvider1.GetDbContext() 位置 C:\xxx\Abp.EntityFramework\EntityFramework\Uow\UnitOfWorkDbContextProvider.cs:行号 28
在 Niue.EntityFramework.EntityFramework.Repositories.SqlRepositories.SqlRepository.get_Context() 位置 C:\xxx\EntityFramework\Repositories\SqlRepositories\SqlRepository.cs:行号 25
在 Niue.EntityFramework.EntityFramework.Repositories.SqlRepositories.SqlRepository.GetDbContext() 位置 C:\xxx\EntityFramework\Repositories\SqlRepositories\SqlRepository.cs:行号 29
在 Niue.EntityFramework.EntityFramework.Repositories.SqlRepositories.SqlRepository.ExecuteGenericsList[T](String sql) 位置 C:\xxx\EntityFramework\Repositories\SqlRepositories\SqlRepository.cs:行号 39
在 Niue.EntityFramework.EntityFramework.Repositories.xxxRepository.FindByOuterId(Int32 masterId, String outerId) 位置 C:\xxx\EntityFramework\Repositories\xxxRepository.cs:行号 156

解决方法：在方法前加上virtual就行了。

	[UnitOfWork]
	public virtual List<T> ExecuteGenericsList<T>(string sql) where T : class, new()
	{
	    var db = _dbContextProvider.GetDbContext().Database;
	    var query = db.SqlQuery<T>(sql);
	    return query.ToList();
	}

下面贴上SqlRepository代码。

    public interface ISqlRepository<TDbContext> : ITransientDependency
    {
        /// 

        /// 执行命令
        /// 
        /// 命令字符串
        /// 执行命令后由数据库返回的结果
        int Execute(string sql);

        /// 

        /// 执行泛型列表查询
        /// 
        /// 
        /// 命令字符串
        /// 泛型列表
        List<T> ExecuteGenericsList<T>(string sql) where T : class, new();

        T ExecuteScalar<T>(string sql);

        /// 

        /// 执行命令
        /// 
        /// 命令字符串
        /// 执行命令后由数据库返回的结果
        Task<int> ExecuteAsync(string sql);

        /// 

        /// 执行泛型列表查询
        /// 
        /// 
        /// 命令字符串
        /// 泛型列表
        Task<List<T>> ExecuteGenericsListAsync<T>(string sql) where T : class, new();

        Task<List<T>> ExecuteGenericsPageListAsync<T, TPagination>(TPagination pagination) where T : class, new() where TPagination : SqlPagination;

        Task<T> ExecuteScalarAsync<T>(string sql);
    }

    public class SqlRepository<TDbContext> : ISqlRepository<TDbContext>, IRepositoryWithDbContext
        where TDbContext : DbContext
    {
        private readonly IDbContextProvider<TDbContext> _dbContextProvider;

        public SqlRepository(IDbContextProvider<TDbContext> dbContextProvider)
        {
            _dbContextProvider = dbContextProvider;
        }

        /// 

        /// Gets EF DbContext object.
        /// 
        public virtual TDbContext Context { get { return _dbContextProvider.GetDbContext(); } }

        public virtual DbContext GetDbContext()
        {
            return Context;
        }

        [UnitOfWork]
        public virtual int Execute(string sql)
        {
            return _dbContextProvider.GetDbContext().Database.ExecuteSqlCommand(sql);
        }

        [UnitOfWork]
        public virtual List<T> ExecuteGenericsList<T>(string sql) where T : class, new()
        {
            var db = _dbContextProvider.GetDbContext().Database;
            var query = db.SqlQuery<T>(sql);
            return query.ToList();
        }

        [UnitOfWork]
        public virtual T ExecuteScalar<T>(string sql)
        {
            var db = _dbContextProvider.GetDbContext().Database;
            var query = db.SqlQuery<T>(sql);
            return query.FirstOrDefault();
        }

        [UnitOfWork]
        public virtual async Task<int> ExecuteAsync(string sql)
        {
            return await _dbContextProvider.GetDbContext().Database.ExecuteSqlCommandAsync(sql);
        }

        [UnitOfWork]
        public virtual async Task<List<T>> ExecuteGenericsListAsync<T>(string sql) where T : class, new()
        {
            var db = _dbContextProvider.GetDbContext().Database;
            var query = db.SqlQuery<T>(sql);
            return await query.ToListAsync();
        }

        [UnitOfWork]
        public virtual async Task<List<T>> ExecuteGenericsPageListAsync<T, TPagination>(TPagination pagination) where T : class, new() where TPagination : SqlPagination
        {
            if (string.IsNullOrWhiteSpace(pagination.Sql))
            {
                return new List<T>();
            }

            var db = _dbContextProvider.GetDbContext().Database;

            StringBuilder sb = new StringBuilder();
            var versonQuery = db.SqlQuery<int>("SELECT CASE WHEN SERVERPROPERTY('productversion') > '11' THEN 1 ELSE 0 END");
            var verson = await versonQuery.FirstOrDefaultAsync();
            if (verson > 0)
            {
                //SQL SERVER 2012 以上版本
                if (pagination.Sql.TrimStart().ToUpper().StartsWith("WITH"))
                {
                    Match match = Regex.Match(pagination.Sql, @"(W|w)(I|i)(T|t)(H|h)(\S|\s)*(A|a)(S|s)(\s)*(\S|\s)*\)(\s)*SELECT");
                    int index = (pagination.PageNo - 1) * pagination.PageSize; //第一条数据的索引
                    sb.Append(match.Value.Substring(0, match.Value.Length - 6));
                    sb.Append(", pagelist AS ( ");
                    sb.Append("	" + pagination.Sql.Replace(match.Value, "SELECT") + " ");
                    sb.Append(") ");
                    sb.Append("SELECT * FROM pagelist ORDER BY " + pagination.Order + " OFFSET " + index + " ROWS FETCH NEXT " + pagination.PageSize + " ROWS ONLY ");
                }
                else
                {
                    int index = (pagination.PageNo - 1) * pagination.PageSize; //第一条数据的索引
                    sb.Append("WITH pagelist AS ( ");
                    sb.Append("	" + pagination.Sql + " ");
                    sb.Append(") ");
                    sb.Append("SELECT * FROM pagelist ORDER BY " + pagination.Order + " OFFSET " + index + " ROWS FETCH NEXT " + pagination.PageSize + " ROWS ONLY ");
                }
            }
            else
            {
                if (pagination.Sql.TrimStart().ToUpper().StartsWith("WITH"))
                {
                    Match match = Regex.Match(pagination.Sql, @"(W|w)(I|i)(T|t)(H|h)(\S|\s)*(A|a)(S|s)(\s)*(\S|\s)*\)(\s)*SELECT");
                    int index = (pagination.PageNo - 1) * pagination.PageSize + 1; //第一条数据的索引
                    sb.Append(match.Value.Substring(0, match.Value.Length - 6));
                    sb.Append(", pagelist AS ( ");
                    sb.Append("	" + pagination.Sql.Replace(match.Value, "SELECT") + " ");
                    sb.Append("), ROW_NUMBER_T AS ( ");
                    sb.Append("	SELECT *,ROW_NUMBER() OVER(ORDER BY " + pagination.Order + ") AS ROW_NUMBER_ID FROM pagelist");
                    sb.Append(") ");
                    sb.Append("SELECT * FROM ROW_NUMBER_T WHERE ROW_NUMBER_ID BETWEEN " + index + " AND " + pagination.PageSize + " ");
                }
                else
                {
                    int index = (pagination.PageNo - 1) * pagination.PageSize + 1; //第一条数据的索引
                    sb.Append("WITH pagelist AS ( ");
                    sb.Append("	" + pagination.Sql + " ");
                    sb.Append("), ROW_NUMBER_T AS ( ");
                    sb.Append("	SELECT *,ROW_NUMBER() OVER(ORDER BY " + pagination.Order + ") AS ROW_NUMBER_ID FROM pagelist");
                    sb.Append(") ");
                    sb.Append("SELECT * FROM ROW_NUMBER_T WHERE ROW_NUMBER_ID BETWEEN " + index + " AND " + pagination.PageSize + " ");
                }
            }

            var query = db.SqlQuery<T>(sb.ToString());
            return await query.ToListAsync();
        }

        [UnitOfWork]
        public virtual async Task<T> ExecuteScalarAsync<T>(string sql)
        {
            var db = _dbContextProvider.GetDbContext().Database;
            var query = db.SqlQuery<T>(sql);
            return await query.FirstOrDefaultAsync();
        }
    }