Question

在我的MVC应用程序中有一个方法

public void insertAddress(AddressModel address)
{
        var connection = OpenConnection();
        var command = connection.CreateCommand();
        command.CommandText = "insert into Adres (AddressLine_1,AddressLine_2,Postcode,Town,DateMovedIn,Id) values (@AddressLine_1, @AddressLine_2, @Postcode, @Town,@DateMovedIn,@Id)";
        AddParameterString(command, "@AddressLine_1", address.AddressLine_1);
        AddParameterString(command, "@AddressLine_2", address.AddressLine_2);
        AddParameterString(command, "@Postcode", address.Postcode);
        AddParameterString(command, "@Town", address.Town);
        AddParameterString(command, "@DateMovedIn", address.DateMovedIn.ToString("yyyyMMdd"));
        AddParameterInt(command, "@Id", address.Id);

        command.ExecuteNonQuery();
}

模型中的

AddressLine2不是必需的。当用户未提交AddressLine2时，我收到错误消息：

参数化查询＆＃39;（@ AddressLine_1 nvarchar（3），@ AddressLine_2 为nvarchar（4000），@ POSTC＆＃39;期望参数＆＃39; @ AddressLine_2＆＃39;，哪个没有提供。

如何在两种情况下修改此方法 - 用户提交AddressLine2而用户未提交AddressLine2？

Answer 1

public void insertAddress(AddressModel address)
{
    var connection = OpenConnection();
    var command = connection.CreateCommand();
    command.CommandText = "insert into Adres (AddressLine_1,AddressLine_2,Postcode,Town,DateMovedIn,Id) values (@AddressLine_1, @AddressLine_2, @Postcode, @Town,@DateMovedIn,@Id)";
    command.Parameters.Add(new SqlParameter { ParameterName = "@AddressLine_1", Value = address.AddressLine_1 });
    if (address.AddressLine_2 == null)
    {
        command.Parameters.Add(new SqlParameter { ParameterName = "@AddressLine_2", Value = DBNull.Value });
    }
    else
    {
        command.Parameters.Add(new SqlParameter { ParameterName = "@AddressLine_2", Value = address.AddressLine_2 });
    }
    command.Parameters.Add(new SqlParameter { ParameterName = "@Postcode", Value = address.Postcode });
    command.Parameters.Add(new SqlParameter { ParameterName = "@Town", Value = address.Town });
    command.Parameters.Add(new SqlParameter { ParameterName = "@DateMovedIn", Value = address.DateMovedIn.ToString("yyyyMMdd") });
    command.Parameters.Add(new SqlParameter { ParameterName = "@Id", Value = address.Id });
    command.ExecuteNonQuery();
}

Answer 2

当参数值为null时会发生这种情况。要修复它，您需要在属性为null时将参数值设置为DbNull。

void AddParameterString(SqlCommand command, string parameterName, string parameterValue)
{
     var param = command.Parameters.Add(parameterName, SqlDbType.NVarChar, 4000);
     param.Value = String.IsNullOrEmpty(parameterValue) ? (object) DbNull.Value : (object) parameterValue;

}

Answer 3

您可以简单地使用Null-coalescing运算符（??）：

AddParameterString(command, "@AddressLine_2", address.AddressLine_2 ?? Convert.DBNull);

参数化查询需要参数，该参数未提供

3 个答案: