The specified conversion is invalid !! Online etc ...

sunnyppp · Post time: 2020-2-17 14:00:01

The following piece of code appears:
"System.InvalidCastException: The specified conversion is invalid."
Troubleshooting tips:
"When a number is coerced, the value must be a number less than infinity
Make sure the source type can be converted to the target type "

Ask for help, give points immediately, if the explanation is clear to everyone, I am willing to add points!

public IList <Bbs_PostDetailsInfo> GetPostDetails (string postid)
{
    IList <Bbs_PostDetailsInfo> postlist = new List <Bbs_PostDetailsInfo> ();
    strSql = "SELECT * FROM V_Bbs_PostDetails WHERE Post_Id =" + postid;
    sdr = GetDataReader (strSql);
    while (sdr.Read ())
    {
            postlist.Add (new Bbs_PostDetailsInfo (sdr.GetInt32 (0), sdr.GetString (1), sdr.GetString (2), sdr.GetInt32 (3),
            sdr.GetString (4), sdr.GetString (5), sdr.GetDateTime (6), sdr.GetInt32 (7), sdr.GetString (8), sdr.GetDateTime (9),
            sdr.GetString (10), sdr.GetString (11), sdr.GetString (12), sdr.GetString (13), sdr.GetString (14), sdr.GetString (15),
            sdr.GetInt32 (16), sdr.GetInt32 (17), sdr.GetInt32 (18), sdr.GetInt32 (19), sdr.GetInt32 (20), sdr.GetInt32 (21),
            sdr.GetString (22), sdr.GetDateTime (23), sdr.GetInt32 (24), sdr.GetInt32 (25), sdr.GetString (26), sdr.GetInt32 (27), sdr.GetInt32 (28), sdr .GetInt32 (29)));
    }
    sdr.Close ();
    sdr.Dispose ();
    return postlist;
}

sunnyppp · Post time: 2020-4-19 23:00:01

To avoid null values I changed to:

public IList <Bbs_PostDetailsInfo> GetPostDetails (string postid)
        {
            IList <Bbs_PostDetailsInfo> postlist = new List <Bbs_PostDetailsInfo> ();
            strSql = "SELECT * FROM V_Bbs_PostDetails WHERE Post_Id =" + postid;
            sdr = GetDataReader (strSql);
            while (sdr.Read ())
            {
                postlist.Add (new Bbs_PostDetailsInfo (sdr.IsDBNull (0)? 0: sdr.GetInt32 (0), sdr.IsDBNull (1)? "": sdr.GetString (1), sdr.IsDBNull (2)? "": sdr.GetString (2), sdr.IsDBNull (3)? 0: sdr.GetInt32 (3),
                    sdr.IsDBNull (4)? "": sdr.GetString (4), sdr.IsDBNull (5)? "": sdr.GetString (5), sdr.GetDateTime (6), sdr.IsDBNull (7)? 0: sdr.GetInt32 (7), sdr.IsDBNull (8)? "": sdr.GetString (8), sdr.GetDateTime (9),
                    sdr.IsDBNull (10)? "": sdr.GetString (10), sdr.IsDBNull (11)? "": sdr.GetString (11), sdr.IsDBNull (12)? "": sdr.GetString (12) , sdr.IsDBNull (13)? "": sdr.GetString (13), sdr.IsDBNull (14)? "": sdr.GetString (14), sdr.IsDBNull (15)? "": sdr.GetString (15 ),
                    sdr.IsDBNull (16)? 0: sdr.GetInt32 (16), sdr.IsDBNull (17)? 0: sdr.GetInt32 (17), sdr.IsDBNull (18)? 0: sdr.GetInt32 (18), sdr. IsDBNull (19)? 0: sdr.GetInt32 (19), sdr.IsDBNull (20)? 0: sdr.GetInt32 (20), sdr.IsDBNull (21)? 0: sdr.GetInt32 (21),
                    sdr.IsDBNull (22)? "": sdr.GetString (22), sdr.GetDateTime (23), sdr.IsDBNull (24)? 0: sdr.GetInt32 (24), sdr.IsDBNull (25)? 0: sdr .GetInt32 (25), sdr.IsDBNull (26)? "": Sdr.GetString (26), sdr.IsDBNull (27)? 0: sdr.GetInt32 (27), sdr.IsDBNull (28)? 0: sdr. GetInt32 (28), sdr.IsDBNull (29)? 0: sdr.GetInt32 (29)));
            }
            sdr.Close ();
            sdr.Dispose ();
            return postlist;
        }

The result is the same!

sunnyppp · Post time: 2020-4-20 05:30:01

strSql = "SELECT * FROM V_Bbs_PostDetails WHERE Post_Id =" + postid;
sdr = GetDataReader (strSql);
Smooth execution!
See special values in the result!

shenmue024 · Post time: 2020-4-20 14:30:01

You add the code to determine whether it is null before the GetString method?

shenmue024 · Post time: 2020-4-21 09:00:01

This error is to convert dbnull.value to int or string

shenmue024 · Post time: 2020-4-21 10:00:02

By the way, not only these two types, but conversion to other types is also a mistake.

shenmue024 · Post time: 2020-4-21 11:30:02

Note that there is also a place for GetDateTime

sunnyppp · Post time: 2020-4-21 13:15:01

Can you explain it more clearly?

Go out and buy something to eat

Come back soon!

Haha!

shenmue024 · Post time: 2020-4-21 18:30:01

Every place of value is judged whether it is DBNull.Value.

sunnyppp · Post time: 2020-4-23 17:45:01

Is this the same?
public IList <Bbs_PostDetailsInfo> GetPostDetails (string postid)
{
    IList <Bbs_PostDetailsInfo> postlist = new List <Bbs_PostDetailsInfo> ();
    strSql = "SELECT * FROM V_Bbs_PostDetails WHERE Post_Id =" + postid;
    sdr = GetDataReader (strSql);
    DateTime strda = DateTime.Today;
    while (sdr.Read ())
    {
        postlist.Add (new Bbs_PostDetailsInfo (sdr.IsDBNull (0)? 0: sdr.GetInt32 (0), sdr.IsDBNull (1)? "": sdr.GetString (1), sdr.IsDBNull (2)? sdr.GetString (2), sdr.IsDBNull (3)? 0: sdr.GetInt32 (3),
            sdr.IsDBNull (4)? "": sdr.GetString (4), sdr.IsDBNull (5)? "": sdr.GetString (5), sdr.IsDBNull (6)? strda: sdr.GetDateTime (6), sdr.IsDBNull (7)? 0: sdr.GetInt32 (7), sdr.IsDBNull (8)? "": sdr.GetString (8), sdr.IsDBNull (9)? strda: sdr.GetDateTime (9),
            sdr.IsDBNull (10)? "": sdr.GetString (10), sdr.IsDBNull (11)? "": sdr.GetString (11), sdr.IsDBNull (12)? "": sdr.GetString (12) , sdr.IsDBNull (13)? "": sdr.GetString (13), sdr.IsDBNull (14)? "": sdr.GetString (14), sdr.IsDBNull (15)? "": sdr.GetString (15 ),
            sdr.IsDBNull (16)? 0: sdr.GetInt32 (16), sdr.IsDBNull (17)? 0: sdr.GetInt32 (17), sdr.IsDBNull (18)? 0: sdr.GetInt32 (18), sdr. IsDBNull (19)? 0: sdr.GetInt32 (19), sdr.IsDBNull (20)? 0: sdr.GetInt32 (20), sdr.IsDBNull (21)? 0: sdr.GetInt32 (21),
            sdr.IsDBNull (22)? "": sdr.GetString (22), sdr.IsDBNull (23)? strda: sdr.GetDateTime (23), sdr.IsDBNull (24)? 0: sdr.GetInt32 (24), sdr .IsDBNull (25)? 0: sdr.GetInt32 (25), sdr.IsDBNull (26)? "": Sdr.GetString (26), sdr.IsDBNull (27)? 0: sdr.GetInt32 (27), sdr. IsDBNull (28)? 0: sdr.GetInt32 (28), sdr.IsDBNull (29)? 0: sdr.GetInt32 (29)));
    }
    sdr.Close ();
    sdr.Dispose ();
    return postlist;
}

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