Sending char * to string c#

Question

i have a function with 2 parameters in c. both of them are char *. one of them is input and another one is output and i don' know what should I fill the second one (output) please help me

 // C
 void func1(char * i_szInput , char * o_szOutput)
 {
    printf("%s\n" ,  i_szInput );
    strcpy(o_szOutput , "Hello");
 }

 // C#
 [DllImport("Test.dll")]
 public static void func1([MarshalAs(UnmanagedType.LPStr)] string str1, 
                          [MarshalAs(UnmanagedType.LPStr)] string str2);


// .......

 string str = null;
 func1("mytest" , str);

You should use StringBuilder

Thomas
– Thomas

2012-08-01 07:06:14 +00:00
Commented Aug 1, 2012 at 7:06 — Thomas
– Thomas, Commented Aug 1, 2012 at 7:06

5 revs · Accepted Answer · 2012-08-01 07:44:01Z

1

Use StringBuilder. From MSDN Marshaling Strings

String by reference: Passes strings as In/Out parameters using StringBuilder.

 [DllImport("Test.dll")]
 public static void func1([MarshalAs(UnmanagedType.LPStr)] String str1,
                          [MarshalAs(UnmanagedType.LPStr)] StringBuilder str2);

StringBuilder str = new StringBuilder();
func1("mytest", str);

See Default Marshaling for Strings: Fixed-Length String Buffers (MSDN).

edited Aug 1, 2012 at 7:44

community wiki

5 revs
Ria

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2 Comments

Thomas Over a year ago

@Ria [MarshalAs(UnmanagedType.LPStr), Out()] StringBuilder str2 or [MarshalAs(UnmanagedType.LPStr)] out StringBuilder str2? And shouldn't you define a size for the StringBuilder?

Ria Over a year ago

Buffers Sample MSDN for marshalling unmanaged LPSTR type.

Std_Net · Accepted Answer · 2012-08-01 07:09:46Z

0

Try this:

string str = String.Empty;
func1("mytest", out str);

answered Aug 1, 2012 at 7:09

Std_Net

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