Implicit REF CURSOR Binding

ODP.NET 11g Release 2 (11.2.0.3.0), and higher, enables applications to run stored procedures with REF CURSOR parameters without using explicit binding for these parameters in the .NET code.

For a read-only result set, such as a REF CURSOR using OracleDataReader, REF CURSOR schema information is retrieved automatically.

For some scenarios, such as when updateable REF CURSORs or Entity Framework is used, developers need to define the REF CURSOR schema information so that the application can bind the implicit REF CURSOR. Entity Framework applications use implicit REF CURSOR binding to instantiate complex types from REF CURSOR data. Applications must specify REF CURSOR bind and metadata information in the app.config, web.config, or machine.config .NET configuration file.

The attributes supplied in the .NET configuration file are also used when the application requests for schema information from the OracleDataReader object that represents a REF CURSOR. This means that for REF CURSORs that are created using a SELECT from a single table, the application can update that table through the use of OracleDataAdapter and OracleCommandBuilder.

When using the Entity Framework, function imports can return an implicitly-bound REF CURSOR. The REF CURSOR can be returned as a collection of complex types or entity types. To return a complex type collection, the .NET configuration file needs to define the REF CURSOR bind and metadata information. To return an entity type collection, only the bind information needs to be defined in the .NET configuration file.

This section contains the following topics:

Specifying REF CURSOR Bind and Metadata Information in the .NET Configuration File

Specify the REF CURSOR information in the oracle.dataacccess.client configuration section of the .NET configuration file. Use an <add> element for each piece of information. The add element uses name-value attributes to specify REF CURSOR information. Use the following format to specify bind information:

<add name="SchemaName.PackageName.StoredProcedureName.RefCursor.RefCursorParameterPositionOrName" 
value="implicitRefCursor bindinfo='mode=InputOutput|Output|ReturnValue'" />

Use the following format to specify metadata information:

<add name="SchemaName.PackageName.StoredProcedureName.RefCursorMetaData.RefCursorParameterPositionorName.Column.ColumnOrdinal" 
value="implicitRefCursor metadata=AttributesList" />

Each REF CURSOR column needs to have an add element defined for it. For example, if you have a REF CURSOR returning five columns, then you need to define five add elements in the config file.

Each add element contains the name and value attributes. The value attribute must begin with the word implicitRefCursor followed by the bindinfo or metadata attribute for specifying bind or metadata information.

The bindinfo information is used by ODP.NET for binding REF CURSOR parameters. The metadata information is used by ODP.NET to associate the schema information with the appropriate REF CURSOR. The metadata comprises of an attributes list that includes parameters together with their values.

The SchemaName, PackageName, and StoredProcedureName are case-sensitive. In order to run a stored procedure with implicit REF CURSOR binding, the SchemaName.PackageName.StoredProcedureName portion of the name attribute must exactly match the name specified in the data dictionary for that stored procedure.

Note:

If the application uses implicit REF CURSOR binding feature outside of Entity Framework, then the .NET configuration file and OracleCommand CommandText do not require the schema name concatenated before the stored procedure name.

If any schema, package, or stored procedure name in the database contains lowercase characters, then it must be enclosed within double quotation marks (") in the config file to preserve the case. Double quotation marks are used within the name attribute by using &quot; when needed. For example, if the schema name is HrSchema, the package name is HrPackage, and the stored procedure name is HrStoredProcedure in the database, the config file should use the following:

<add name="&quot;HrSchema&quot;.&quot;HrPackage&quot;.&quot;HrStoredProcedure&quot;.RefCursorMetaData . . . />

By default, Oracle Database stores these names as uppercase characters. ODP.NET assumes default behavior, and converts all names to uppercase characters unless you explicitly preserve the case by using double quotation marks.

Note:

The SchemaName, PackageName, StoredProcedureName, or ParameterName cannot contain a period (".") in the name. For example, P.0 is an unacceptable parameter name.

Depending on whether the application uses bind-by-name or bind-by-position, the RefCursorParameterPositionOrName portion of the name attribute must be set with the correct parameter position (for bind by position) or parameter name (for bind by name). For functions, the position is 0-based, where the position 0 represents the return value. For procedures, the position is 1-based, as there are no return values for procedures. For example, if a stored procedure accepts five parameters, returning only two REF CURSORs in the third and fifth parameter positions, then the .NET config REF CURSOR bind information should contain one entry for position 3 and one entry for position 5.

If bind-by-name is used, the attribute name is used to identify the REF CURSOR parameter. The name should use the same name and case as the one specified in the data dictionary for that stored procedure.

For bindinfo, the mode specifies the parameter direction of the parameter. The mode must be either InputOutput, Output, or ReturnValue.

Note:

Implicit REF CURSOR binding for an input REF CURSOR parameter is not supported.

An exception is thrown at runtime if the .NET configuration file contains an entry for a REF CURSOR whose mode is set to Input.

For metadata, The AttributesList contains the list of parameters. Table 3-16 describes the parameters that can be included in the AttributesList.

Example 3-2 shows a sample add element that uses bindinfo. Here, the schema name is SCOTT and the stored procedure name is TESTPROC. The parameter name is parameter1. The mode is output.

Example 3-2 Using the add Element with bindinfo

<add name="SCOTT.TESTPROC.RefCursor.parameter1" value="implicitRefCursor
 bindinfo='mode=Output'" />

Example 3-3 shows a sample add element that uses metadata.

Example 3-3 Using the add Element with metadata

<add name="scott.TestProc.RefCursorMetaData.parameter1.Column.0" 
value="implicitRefCursor metadata='ColumnName=EMPNO;BaseColumnName=EMPNO;
BaseSchemaName=SCOTT;BaseTableName=EMP;NativeDataType=number;
ProviderType=Int32;DataType=System.Int32;ColumnSize=4;AllowDBNull=false;
IsKey=true'" />

Table 3-16 Allowed Parameters in Attributes List

Name Type Required/Optional for Entity Framework Description

ColumnName

System.String

Required

The name of the column.

ProviderType

Oracle.DataAccess.Client.OracleDbType

Required

The database column type (OracleDbType) of the column

NativeDataType

System.String

Required

The Oracle type. For example, NCLOB.

BaseColumnName

System.String

Optional

The name of the column in the database if an alias is used for the column.

BaseSchemaName

System.String

Optional

The name of the schema in the database that contains the column.

BaseTableName

System.String

Optional

The name of the table or view in the database that contains the column.

ColumnSize

System.Int64

Optional

The maximum possible length of a value in the column

NumericPrecision

System.Int16

Optional

The maximum precision of the column, if the column is a numeric data type.

NumericScale

System.Int16

Optional

The maximum scale of the column, if the column is a numeric data type.

IsUnique

System.Boolean

Optional

Indicates whether or not the column is unique.

IsKey

System.Boolean

Optional

Indicates whether or not the column is a key column. For a table to be updated with the REF CURSOR information, at least one of the columns in the REF CURSOR metadata should have this value set to true

IsRowID

System.Boolean

Optional

true if the column is a ROWID, otherwise false.

DataType

System.RuntimeType

Optional

Maps to the common language runtime type.

AllowDBNull

System.Boolean

Optional

true if null values are allowed, otherwise false

IsAliased

System.Boolean

Optional

true if the column is an alias; otherwise false.

IsByteSemantic

System.Boolean

Optional

IsByteSemantic is:

  • true if the ColumnSize value uses bytes semantics

  • false if ColumnSize uses character semantics

IsExpression

System.Boolean

Optional

true if the column is an expression, else false.

IsHidden

System.Boolean

Optional

true if the column is hidden, else false.

IsReadOnly

System.Boolean

Optional

true if the column is read-only, else false

IsLong

System.Boolean

Optional

true if the column is of LONG, LONG RAW, BLOB, CLOB, or

BFILE type, else false.

UdtTypeName

System.String

Optional

The type name of the UDT.

ProviderDBType

System.Data.DbType

Optional

System.Data.DbType

ObjectName

System.String

Optional

Represents the name of the object.


Some of the attributes, listed in Table 3-16, automatically have their values set using the result set's metadata. Developers can override these default values by setting a value explicitly.

You may have to explicitly define some attributes listed as optional for certain operations. For example, updateable REF CURSOR requires the developer to define key information.

Sample Configuration File and Application

This section builds a sample application to illustrate implicit REF CURSOR binding. It contains the following topics:

Sample Stored Procedure and Function

CREATE OR REPLACE FUNCTION GETEMP (
  EMPID IN NUMBER) return sys_refcursor is
  emp sys_refcursor;
BEGIN
  OPEN emp FOR SELECT empno, ename FROM emp where empno = EMPID;
  return emp;
END;
/
 
CREATE OR REPLACE PROCEDURE "GetEmpAndDept" (
  EMPS OUT sys_refcursor,
  DEPTS OUT sys_refcursor) AS
BEGIN
  OPEN EMPS for SELECT empno, ename from emp;
  OPEN DEPTS for SELECT deptno, dname from dept;
END;
/

Sample Application Configuration File

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <oracle.dataaccess.client>
    <settings>
 
      <!-- The following is for SCOTT.GETEMP -->
      <add name="SCOTT.GETEMP.RefCursor.0" 
           value="implicitRefCursor bindinfo='mode=ReturnValue'" />
 
      <!-- The following is for SCOTT.GETEMP's REF CURSOR metadata -->
      <add name="SCOTT.GETEMP.RefCursorMetaData.0.Column.0"
           value="implicitRefCursor metadata='ColumnName=EMPNO;
           BaseColumnName=EMPNO;BaseSchemaName=SCOTT;BaseTableName=EMP;
           NativeDataType=number;ProviderType=Int32;ProviderDBType=Int32;
           DataType=System.Int32;ColumnSize=4;NumericPrecision=10;
           NumericScale=3;AllowDBNull=false;IsKey=true'" />
 
      <add name="SCOTT.GETEMP.RefCursorMetaData.0.Column.1"
           value="implicitRefCursor metadata='ColumnName=ENAME;
           BaseColumnName=ENAME;BaseSchemaName=SCOTT;BaseTableName=EMP;
           NativeDataType=varchar2;ProviderType=Varchar2;
           ProviderDBType=String;DataType=System.String;
           ColumnSize=10;AllowDBNull=true'" />
 
      <!-- The following is for "SCOTT"."GetEmpAndDept" -->
      <add name="SCOTT.&quot;GetEmpAndDept&quot;.RefCursor.EMPS" 
           value="implicitRefCursor bindinfo='mode=Output'" />
 
      <!-- The following is for SCOTT.GETEMP's EMPS REF CURSOR metadata -->
      <add name="SCOTT.&quot;GetEmpAndDept&quot;
           .RefCursorMetaData.EMPS.Column.0"
           value="implicitRefCursor metadata='ColumnName=EMPNO;
           BaseColumnName=EMPNO;BaseSchemaName=SCOTT;BaseTableName=EMP;
           NativeDataType=number;ProviderType=Int32;ProviderDBType=Int32;
           DataType=System.Int32;ColumnSize=4;NumericPrecision=10;
           NumericScale=3;AllowDBNull=false;IsKey=true'" />
 
      <add name="SCOTT.&quot;GetEmpAndDept&quot;
           .RefCursorMetaData.EMPS.Column.1"
           value="implicitRefCursor metadata='ColumnName=ENAME;
           BaseColumnName=ENAME;BaseSchemaName=SCOTT;BaseTableName=EMP;
           NativeDataType=varchar2;ProviderType=Varchar2;
           ProviderDBType=String;DataType=System.String;
           ColumnSize=10;AllowDBNull=true'" />
 
      <!-- The following is for SCOTT.GETEMP's DEPTS REF CURSOR metadata -->
      <add name="SCOTT.&quot;GetEmpAndDept&quot;.RefCursor.DEPTS" 
           value="implicitRefCursor bindinfo='mode=Output'" />
 
      <add name="SCOTT.&quot;GetEmpAndDept&quot;
           .RefCursorMetaData.DEPTS.Column.0"
           value="implicitRefCursor metadata='ColumnName=DEPTNO;
           BaseColumnName=DEPTNO;BaseSchemaName=SCOTT;BaseTableName=DEPT;
           NativeDataType=number;ProviderType=Int32;ProviderDBType=Int32;
           DataType=System.Int32;ColumnSize=4;NumericPrecision=10;
           NumericScale=3;AllowDBNull=false;IsKey=true'" />
 
      <add name="SCOTT.&quot;GetEmpAndDept&quot;
           .RefCursorMetaData.DEPTS.Column.1"
           value="implicitRefCursor metadata='ColumnName=DNAME;
           BaseColumnName=DNAME;BaseSchemaName=SCOTT;BaseTableName=DEPT;
           NativeDataType=varchar2;ProviderType=Varchar2;
           ProviderDBType=String;DataType=System.String;
           ColumnSize=10;AllowDBNull=true'" />
      </settings>
  </oracle.dataaccess.client>
</configuration>

Sample Application That Uses the Configuration File

using System;
using System.Data;
using Oracle.DataAccess.Client;
 
class Program
{
  static void Main(string[] args)
  {
    try
    {
      // Open a connection
      string constr =
        "User Id=scott;Password=tiger;Data Source=inst1";
      OracleConnection con = new OracleConnection(constr);
      con.Open();
 
      // Use implicit REF CURSOR binding 
      //   to execute SCOTT.GETEMP function
      // Use bind by position as configured 
      //   in app.config for SCOT.GETEMP
      OracleCommand cmd = con.CreateCommand();
      cmd.CommandText = "SCOTT.GETEMP";
      cmd.CommandType = CommandType.StoredProcedure;
      cmd.BindByName = false;
      OracleParameter empid = cmd.Parameters.Add("empid", 
        OracleDbType.Int32, ParameterDirection.Input);
      empid.Value = 7654;
 
      // Populate the DataSet
      OracleDataAdapter adapter = new OracleDataAdapter(cmd);
      DataSet ds = new DataSet();
      adapter.Fill(ds);
      Console.WriteLine("Retrieved {0} row from EMP", 
        ds.Tables[0].Rows.Count);
 
      // Use implicit REF CURSOR binding 
      //   to execute "SCOTT"."GetEmpAndDept" procedure
      // Use bind by name as configured 
      //   in app.config for "SCOTT"."GetEmpAndDept"
      cmd = con.CreateCommand();
      cmd.CommandText = "\"SCOTT\".\"GetEmpAndDept\"";
      cmd.CommandType = CommandType.StoredProcedure;
      cmd.BindByName = true;
      adapter = new OracleDataAdapter(cmd);
      adapter.Fill(ds);
      Console.WriteLine("Retrieved {0} rows from DEPT", 
        ds.Tables[1].Rows.Count);
    }
    catch (Exception ex)
    {
      // Output the message
      Console.WriteLine(ex.Message);
      if (ex.InnerException != null)
      {
        // If any details are available regarding
        // errors in the app.config, print them out
        Console.WriteLine(ex.InnerException.Message);
        if (ex.InnerException.InnerException != null)
        {
          Console.WriteLine(
            ex.InnerException.InnerException.Message);
        }
      }
    }
  }
}

Usage Considerations

This section discusses the following usage considerations when using implicit REF CURSOR:

CommandText Property Considerations

ODP.NET applications should ensure that the stored procedure name and the OracleCommand CommandText match exactly. Let's take a scenario where the stored procedure name in the database is SCOTT.TESTPROC. Now, if the CommandText uses TESTPROC, ODP.NET will look for entries matching TESTPROC only. The current schema name will not be automatically appended to TESTPROC. So, the correct CommandText to use in this scenario would be SCOTT.TESTPROC.

Also, the CommandText is case-sensitive and must use the same case as the stored procedure name in the database. So if the stored procedure name in the database is SCOTT.Testproc, then the CommandText must use SCOTT.Testproc.

Bind Considerations

If information about a REF CURSOR parameter has been added to the configuration file, then applications should not try to explicitly bind the REF CURSOR parameter to OracleCommand. ODP.NET automatically binds the REF CURSOR parameter at the appropriate locations based on the information provided in the configuration file. If the application stored procedure also has non-REF CURSOR parameters, then these parameters must still be explicitly bound to OracleCommand.

If the information specified in the configuration file for a stored procedure identifies the REF CURSOR parameter by name, then all the other non-REF CURSOR parameters should also be bound by name. Also the BindByName property for the OracleCommand object should be set to true in this case. Entity Framework always uses BindByName to run stored procedures. Your .NET configuration file parameter names must use the same case that was used when creating the stored procedure in the database.

If the OracleCommand BindByName property is set to false (default), then ODP.NET assumes that the parameters have been bound based on their position, and all parameters have been specified in the correct order. For such cases, the parameters specified in the configuration file are bound in the same order in which they appear in the configuration file.

Overloaded Stored Procedures

ODP.NET does not support multiple stored procedures with the same name inside the configuration file. If an ODP.NET application uses an overloaded stored procedure, the application can store only one overloaded stored procedure information in the configuration file.

Type Initialization Exceptions

Type initialization exceptions can be caused by invalid .NET configuration file entries. Evaluate the exception that is caught as well as its inner exceptions to determine the .NET configuration file entry or the attribute setting that is causing the exception.

ODP.NET tracing logs the valid and invalid .NET configuration file entries that ODP.NET has parsed. To look for .NET configuration file related entries, set the TraceLevel to the Entry, exit, and SQL statement information level setting. Trace entries related to implicit REF CURSOR binding have a (REFCURSOR) entry along with (ERROR), if any errors are encountered.

Using Stored Functions with Function Import

Function Import only supports stored procedures, and does not support functions. When using the Add Function Import dialog for the Entity Data Model that you have created, the Get Column Information button does not return the metadata information for the REF CURSOR that is being returned by a stored function, even if it is configured properly in the .NET configuration file.