Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
746 views
in Technique[技术] by (71.8m points)

c# - Type of conditional expression cannot be determined because there is no implicit conversion between 'string' and 'System.DBNull'

param7[1].Value = tbLastName.Text.Length > 0 ? tbLastName.Text : DBNull.Value;

Why is this impossible, and any suggestion what else to try? If/else for 20 parameters is just not way.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

The issue is that (as the error message indicates) the conditional expression needs either identical types on both branches, or else there needs to be an implicit conversion from one of the types to the other. In your case, there isn't one, and so you get the error. One quick fix would be cast one of the values to (object) (which is fine, since DbParameter.Value is of type object anyway.)

So this should work for you:

param7[1].Value = tbLastName.Text.Length > 0 ? tbLastName.Text : (object)DBNull.Value;

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...