VB.NET assigning string value ---- String1 = String1+String2

Question

Back in VB6, you were able to re-assign a string's value to itself plus other string values, such as:

str_Duplications_Line = str_Duplications_Line & pRow_Prime.Value(i_FieldNum)

Now, intellisense is not picking it up as an error, nor is the compiler complaining, but when it is ran, it bombs out on that line, and other multiple line such as these:

str_Duplications_Line = str_Duplications_Line & ","

str_Duplications_AllFields = str_Duplications_AllFields + str_Duplications_Line + vbCrLf

Any idea why this is happening, and how I can fix this? Or at least, simulate the same thing in VB.NET?

"Bombs out"? Is there an error? Errors usually contain useful information about what went wrong. Both the `+` and `&` operators can be used to concatenate strings. Somewhat related: http://stackoverflow.com/questions/3006153/vb-net-ampersand-vs-plus-for-concatenating-string — David, May 19 '12 at 23:16
What do you mean by `bombs out` ? What error are you getting? — jams, May 19 '12 at 23:27

score 3 · Accepted Answer · answered May 19 '12 at 23:34

3

Here is the diference between & and +

"abc" + "def" = "abcdef"
"abc" & "def" = "abcdef"
"111" + "222" = "111222"
"111" & "222" = "111222"
"111" & 222 = "111222"
"111" + 222 = 333
"abc" + 222 = conversion error

If any one operand is null, you may get an error.

answered May 19 '12 at 23:34

Krishanu Dey

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Of course if you have Option Strict On `"111" + 222` and `"abc" + 222` will not compile – Matt Wilko May 21 '12 at 10:23

score 2 · Answer 2 · answered May 19 '12 at 23:20

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Make sure you're not trying to concatenate a null to your string

answered May 19 '12 at 23:20

web_bod

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I will do an if-then statement to make sure it does not assign nulls thank you! – Logan B. Lehman May 19 '12 at 23:29
But isn't it legal to concatenate null to a string in VB? AFAICR null is treated as empty string "" – MarkJ May 20 '12 at 12:10

VB.NET assigning string value ---- String1 = String1+String2

2 Answers2