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C# - Manipulating SqlDataReader Process

Posted on 2007-11-22
10
1,941 Views
Last Modified: 2008-02-01
Dear Experts,

Do anyone know how to manipulate the process so I don't have to write all the fields manually?
I wonder if I can use loop on the dataReader by using dataReader.VisibleFieldCount and get the field name by dataReader.GetName().

as you can see the object name is the same as the dataReader's field name, but the case is not same.
The myTable field object using proper case and the dataReader field's name using camel case.

I hope my description are clear enough. Sorry my english is not very good since english is not my first language :).

Thanks you.

Kind Regards,
Aciang
System.Data.SqlClient.SqlDataReader dataReader = null;
 
dataReader = getDate()
 
while (dataReader.Read())
{
	myTable = new MyTable()
	
	myTable.CustNo = dataReader["custNo"];
	myTable.CustName = dataReader["custName"];
	mytable.CustAddress = dataReader["custAddress"];
	myTable.PhoneNo = dataReader["phoneNo"];
	...
	...
}

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Question by:aciang
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10 Comments
 
LVL 39

Expert Comment

by:Pratima Pharande
ID: 20337359
You can use like this if you know the correct indexes of fields

myTable.CustNo = dataReader[0];               //First column value
	myTable.CustName = dataReader[1];     //2nd
	mytable.CustAddress = dataReader[2];
	myTable.PhoneNo = dataReader[3];

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LVL 39

Expert Comment

by:Pratima Pharande
ID: 20337376
Or you can try like this

For string fields

dataReader.GetString(0).ToString
dataReader.GetString(1).ToString

For int

dataReader.GetInt32(0)

and so on


0
 

Author Comment

by:aciang
ID: 20337495
Thank you for the answer 'Pratima'
is there another way that I don't have to write down all the MyTable properties like CustName, CustAddress, etc..
If I have 50 properties on MyTable, it means I have to write 50 statements.
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LVL 16

Expert Comment

by:gnoon
ID: 20337539
Sound like you need some classes in System.Reflection. Try this

Type t;
FieldInfo[] f;
while (dataReader.Read())
{
	myTable = new MyTable();
 
	t = n.GetType();
	f = t.GetFields(BindingFlags.Public|BindingFlags.Instance);
	for(int i=0; i<f.Length; i++)
	{
		f[i].SetValue(myTable, dataReader[f[i].Name]);
	}
}

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LVL 16

Expert Comment

by:gnoon
ID: 20337542
Sorry

t = n.GetType();

should be

t = myTable .GetType();
0
 

Author Comment

by:aciang
ID: 20337792
Thank you 'gnoon'
it almost solve my problem. I change the code like below.
myObject has more properties than dataReader's fields,
and I don't know how to validate if myObject property's name match with dataReader's fieldname. so for temporary I put try and catch to ignore the error because of the property name and dataReader's field is not match.

is it possible not to loop the MyObject properties?
Can we trigger the DataReader's field Name?

Thank you.

Type t;
PropertyInfo[] p;
 
while (dataReader.Read())
{
	myObject = new MyObject();
	t = myObject.GetType();
	p = t.GetProperties(BindingFlags.Public | BindingFlags.Instance);
	for (int i = 0; i < p.Length; i++)
	{
		try
		{
			p[i].SetValue(myObject, dataReader[p[i].Name], null);
		}
		catch
		{
		}
	}
}

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LVL 16

Accepted Solution

by:
gnoon earned 500 total points
ID: 20337880
>Can we trigger the DataReader's field Name?
Yes, read the name from schema table
Type t;
PropertyInfo p;
DataTable schemaTb = dataReader.GetSchemaTable();
 
while (dataReader.Read())
{
	myObject = new MyObject();
	t = myObject.GetType();
	foreach(DataRow row in schemaTb.Rows)
	{
		p = GetPropertyInfo(t, row("ColumnName"));
		if(p != null)
			p.SetValue(myObject, dataReader[p.Name], null);
	}
}
 
PropertyInfo GetPropertyInfo(Type t, string dbFieldName)
{
	return t.GetProperty(dbFieldName);
	// GetProperty accepts case-sensitive field name.
	// It may be different from database field.
	// So, you may need to search from array manually (to ignore case)
	// PropertyInfo[] p = t.GetProperties(BindingFlags.Public | BindingFlags.Instance);
	// loop to search for dbFieldName with p[i].Name
}

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Author Comment

by:aciang
ID: 20337961
Sorry 'gnoon',
on this statement:
p = GetPropertyInfo(t, row("ColumnName"));
it returns error:
'row' is a 'variable' but is used like a 'method'

please kindly advise :).
0
 
LVL 16

Expert Comment

by:gnoon
ID: 20338045
Sorry.. I did copy/paste from my VB. Change it to row["ColumnName"] ;-)
0
 

Author Comment

by:aciang
ID: 20341527
Excellent I change it a little to:
p = GetPropertyInfo(t, (string) row["ColumnName"]);

Thank you so much gnoon :).
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