ADO.NET - Size 属性的大小为 0 无效 [英] ADO.NET - The Size property has an invalid size of 0

问题描述

我正在尝试通过 ADO.NET 从 DB 获取输出值.有一个客户端代码:

I'm trying to get output value from DB via ADO.NET. There's a client code:

    using (var connection = new SqlConnection(ConnectionString))
    {
        connection.Open();
        SqlCommand command = new SqlCommand("pDoSomethingParamsRes", connection);
        command.CommandType = CommandType.StoredProcedure;
        command.Parameters.Add("@i", 1);
        var outParam = new SqlParameter("@out", SqlDbType.VarChar);
        outParam.Direction = ParameterDirection.Output;
        command.Parameters.Add(outParam);
        command.ExecuteNonQuery();
        Console.WriteLine(command.Parameters["@out"].Value.ToString());
    }

当我运行它时，我得到以下异常:

When I run this I get the following exception:

the Size property has an invalid size of 0

根据手册 SqlParameter.Size 属性 我可能会省略尺寸.为什么会出现此异常?

According to manual SqlParameter.Size Property I might omit size. Why do I get this exception?

如何在不传递大小的情况下使其工作?

How to make it work without passing size?

推荐答案

VarChar 和 NVarChar 是可变宽度字符字段(因此是 var+char).您必须设置长度，否则默认为零.

VarChar and NVarChar are variable width character fields (thus var+char). You have to set the length, otherwise the default is zero.

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