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OleDbDataReader

OleDbDataReader# DotNet - 窗口里的风景

i*p2008-09-11 07:09

1 楼

OleDbDataReader objDataReader;
...
objDataReader("categoryID")
They are fine in VB, but when I use these code to C#, the error message says:
CS0118: 'objDataReader' is a 'variable' but is used like a 'method'.
How to use OleDbDataReader rightly in C#?
Thanks!

c*e2008-09-11 07:09

2 楼

objDataReader["categoryID"]

says:

【在 i**p 的大作中提到】

: OleDbDataReader objDataReader;
: ...
: objDataReader("categoryID")
: They are fine in VB, but when I use these code to C#, the error message says:
: CS0118: 'objDataReader' is a 'variable' but is used like a 'method'.
: How to use OleDbDataReader rightly in C#?
: Thanks!

i*p2008-09-11 07:09

3 楼

still has error on eventsXMLDoc.WriteAttributeString("id", dataReader["
categoryID"]);
CS1502: The best overloaded method match for 'System.Xml.XmlWriter.
WriteAttributeString(string, string)' has some invalid arguments
Here is the source code.
System.Data.OleDb.OleDbDataReader dataReader =
dbCommand.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
System.Xml.XmlTextWriter eventsXMLDoc = new
System.Xml.XmlTextWriter(Response.OutputStream, Encoding.UTF8);
// generate XM

【在 c**e 的大作中提到】

: objDataReader["categoryID"]
:
: says:

c*e2008-09-11 07:09

4 楼

dataReader["categoryID"] returns an object and not a string
you need to cast it to string

"]

【在 i**p 的大作中提到】

: still has error on eventsXMLDoc.WriteAttributeString("id", dataReader["
: categoryID"]);
: CS1502: The best overloaded method match for 'System.Xml.XmlWriter.
: WriteAttributeString(string, string)' has some invalid arguments
: Here is the source code.
: System.Data.OleDb.OleDbDataReader dataReader =
: dbCommand.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
: System.Xml.XmlTextWriter eventsXMLDoc = new
: System.Xml.XmlTextWriter(Response.OutputStream, Encoding.UTF8);
: // generate XM

i*p2008-09-11 07:09

5 楼

You are really cute! Please help to make me cute too. How to cast it to
string?

【在 c**e 的大作中提到】

: dataReader["categoryID"] returns an object and not a string
: you need to cast it to string
:
: "]

a*x2008-09-11 07:09

6 楼

tostring

【在 i**p 的大作中提到】

: You are really cute! Please help to make me cute too. How to cast it to
: string?

i*p2008-09-11 07:09

7 楼

dataReader["categoryID"].ToString() ?
But when I use this in VB, it works without the cast.

【在 a***x 的大作中提到】

: tostring

c*e2008-09-11 07:09

8 楼

(string)dataReader["categoryID"]

【在 i**p 的大作中提到】

: You are really cute! Please help to make me cute too. How to cast it to
: string?

c*e2008-09-11 07:09

9 楼

turn on Option Strict on your VB code and see what happens

【在 i**p 的大作中提到】

: dataReader["categoryID"].ToString() ?
: But when I use this in VB, it works without the cast.

i*p2008-09-11 07:09

10 楼

you are not cute this time.
[InvalidCastException: Unable to cast object of type 'System.Int32' to type
'System.String'.]
dataReader["categoryID"].ToString() works.

【在 c**e 的大作中提到】

: (string)dataReader["categoryID"]

k*e2008-09-11 07:09

11 楼

you need to know the type of data in your dataReader!

type

【在 i**p 的大作中提到】

: you are not cute this time.
: [InvalidCastException: Unable to cast object of type 'System.Int32' to type
: 'System.String'.]
: dataReader["categoryID"].ToString() works.

E*A2008-09-11 07:09

12 楼

int id =(int)(dataReader.IsDBNull() ? 0 : dataReader.GetInt32(i));
//i 代表 categoryID 在SQL查询语句中的顺序
eventsXMLDoc.WriteAttributeString("id", id.ToString());