cannot convert from type to type.

[Guest]

Hi,

I have the following procedure below:
I am getting 2 errors on compile:

Argument '2': cannot convert from 'System.Data.SqlClient.SqlDataReader' to
'ref System.Data.SqlClient.SqlDataReader'

Argument '3': cannot convert from 'System.Text.StringBuilder' to 'ref
System.Text.StringBuilder'

the PrintChildrenRecursive is a class in a referenced DLL that was written in
VB.NET.

this function takes a dataset and loops through it creating a javastring
using stringbuilder that creates a parent-child tree of html hyperlinks.

the printchildrecursive function accepts the Dr and Sbuilder ByReference.

private static void PrintFromRoot(SqlDataReader Dr, StringBuilder SBuilder)
{
PrintChildren PCR = new PrintChildren();

SBuilder.Append("[");
PCR.PrintChildrenRecursive(1, Dr, SBuilder, false);

SBuilder.Remove(1,2); //remove comma and bracket from beginning of string

SBuilder.Append("];");
}

I don't understand why conversion is occuring because they are already of
the correct type as already indicated by the error messages.

thanks

Chris

 

[Nicholas Paldino [.NET/C# MVP]]

Chris,

You are passing parameters by reference. In order to do so, you need to
use the ref keyword, like this:

obj.PrintFromRoot(ref sqlDataReader, ref stringBuilder);

Hope this helps.

 

[Guest]

Nicholas,

thank you so much!

Chris,

You are passing parameters by reference. In order to do so, you need to
use the ref keyword, like this:

obj.PrintFromRoot(ref sqlDataReader, ref stringBuilder);

Hope this helps.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

Hi,

I have the following procedure below:
I am getting 2 errors on compile:

Argument '2': cannot convert from 'System.Data.SqlClient.SqlDataReader' to
'ref System.Data.SqlClient.SqlDataReader'

Argument '3': cannot convert from 'System.Text.StringBuilder' to 'ref
System.Text.StringBuilder'

the PrintChildrenRecursive is a class in a referenced DLL that was written
in
VB.NET.

this function takes a dataset and loops through it creating a javastring
using stringbuilder that creates a parent-child tree of html hyperlinks.

the printchildrecursive function accepts the Dr and Sbuilder ByReference.

private static void PrintFromRoot(SqlDataReader Dr, StringBuilder
SBuilder)
{
PrintChildren PCR = new PrintChildren();

SBuilder.Append("[");
PCR.PrintChildrenRecursive(1, Dr, SBuilder, false);

SBuilder.Remove(1,2); //remove comma and bracket from beginning of string

SBuilder.Append("];");
}

I don't understand why conversion is occuring because they are already of
the correct type as already indicated by the error messages.

thanks

Chris

 

[Jon Skeet [C# MVP]]

Nicholas,

thank you so much!

Note, however, that you very rarely really want to pass a StringBuilder
or a SqlDataReader by reference. Seeing code which does is *usually* an
indication of a lack of understanding of reference types and parameter
passing.

See http://www.pobox.com/~skeet/csharp/parameters.html for more
information.