c# - 参数化查询 ..... 需要参数 '@units' ，但未提供

Question

我遇到了这个异常:

The parameterized query '(@Name nvarchar(8),@type nvarchar(8),@units nvarchar(4000),@rang' expects the parameter '@units', which was not supplied.

我的插入代码是:

public int insertType(string name, string type, string units = "N\\A", string range = "N\\A", string scale = "N\\A", string description = "N\\A", Guid guid = new Guid())
{
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();
        SqlCommand command = new SqlCommand();
        command.CommandText = "INSERT INTO Type(name, type, units, range, scale, description, guid) OUTPUT INSERTED.ID VALUES (@Name, @type, @units, @range, @scale, @description, @guid) ";
        command.Connection = connection;
        command.Parameters.AddWithValue("@Name", name);
        command.Parameters.AddWithValue("@type", type);
        command.Parameters.AddWithValue("@units", units);
        command.Parameters.AddWithValue("@range", range);
        command.Parameters.AddWithValue("@scale", scale);
        command.Parameters.AddWithValue("@description", description);
        command.Parameters.AddWithValue("@guid", guid);
        return (int)command.ExecuteScalar();
    }
}

异常是一个惊喜，因为我正在使用 AddWithValue 函数并确保我为该函数添加了一个默认参数。

已解决:

问题是某些参数为空字符串(覆盖默认值)

这是工作代码:

public int insertType(string name, string type, string units = "N\\A", string range = "N\\A", string scale = "N\\A", string description = "N\\A", Guid guid = new Guid())
    {
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();
            SqlCommand command = new SqlCommand();
            command.CommandText = "INSERT INTO Type(name, type, units, range, scale, description, guid) OUTPUT INSERTED.ID VALUES (@Name, @type, @units, @range, @scale, @description, @guid) ";
            command.Connection = connection;
            command.Parameters.AddWithValue("@Name", name);
            command.Parameters.AddWithValue("@type", type);

            if (String.IsNullOrEmpty(units))
            {
                command.Parameters.AddWithValue("@units", DBNull.Value); 
            }
            else
                command.Parameters.AddWithValue("@units", units);
            if (String.IsNullOrEmpty(range))
            {
                command.Parameters.AddWithValue("@range", DBNull.Value);
            }
            else
                command.Parameters.AddWithValue("@range", range);
            if (String.IsNullOrEmpty(scale))
            {
                command.Parameters.AddWithValue("@scale", DBNull.Value);
            }
            else
                command.Parameters.AddWithValue("@scale", scale);
            if (String.IsNullOrEmpty(description))
            {
                command.Parameters.AddWithValue("@description", DBNull.Value);
            }
            else
                command.Parameters.AddWithValue("@description", description);




            command.Parameters.AddWithValue("@guid", guid);


            return (int)command.ExecuteScalar();
        }


    }

Answer 1

试试这段代码:

SqlParameter unitsParam = command.Parameters.AddWithValue("@units", units);
if (units == null)
{
    unitsParam.Value = DBNull.Value;
}

并且您必须检查所有其他参数是否为空值。如果它为 null，则必须传递 DBNull.Value 值。