ColdFusion converts data automatically among ColdFusion, Java, and CLR data types. The following table indicates how ColdFusion converts among .NET Common Language Runtime (CLR) primitive and standard data types, the Java data types used in the proxies to represent CLR data types, and ColdFusion data types in your CFML application.

Use the JavaCast function to convert ColdFusion data into BigDecimal format before you pass the value to a .NET function, as in the following example:

<cfset netObj.netFunc(javacast("bigdecimal","439732984732048"))>

ColdFusion automatically converts returned decimal and System.Decimal values to ColdFusion string representations.

ColdFusion converts .NET decimal or System.Decimal types only if the proxy for System.Decimal is a value type proxy. Similarly, it converts .NET System.DateTime values to ColdFusion Date-time values only if the proxy for System.DateTime is a value type proxy. The ColdFusion server always uses value proxies when it generates these proxies. If you use the JNBProxyGUI.exe tool to generate the proxy, however, make sure to generate the proxy for System.Decimal as value type.

When a .NET method specifies System.Object (as opposed to a specific Object subclass, such as System.Boolean) as the argument type, and you want to pass primitive values as arguments to that method, use the javacast function to identify the data conversion. Once ColdFusion knows the data type, it automatically converts to the appropriate .NET type. Here is the table that describes the conversion rule from ColdFusion type to .NET type.

Create special objects for .NET primitive unsigned data types, such as byte (unsigned byte), ushort (unsigned short), uint (unsigned int) and ulong (unsigned long), for which no corresponding java types exist. The following table lists the .NET primitive types and the corresponding class you must use.

Use the createObject function or cfobject tag to create these special objects, in the same manner as you create other .NET classes, before you use them in your assignment statement. For example, the following line creates a ushort representation of the value 100:

<cfset boxedUShort = createObject(".NET". "System.BoxedUShort").init(100)>

The following example creates a System.Hashtable object and populates it with examples of all types of primitives.

<!--- create a .NET Hashtable ---> 
<cfset table = createObject(".NET", "System.Collections.Hashtable")> 
 
<!--- call HashTable.add(Object, Object) method for all primitives ---> 
<cfset table.add("shortVar", javacast("short", 10))> 
<cfset table.add("sbyteVar", javacast("byte", 20))> 
<cfset table.add("intVar", javacast("int", 123))> 
<cfset table.add("longVar", javacast("long", 1234))> 
<cfset table.add("floatVar", javacast("float", 123.4))> 
<cfset table.add("doubleVar", javacast("double", 123.4))> 
<cfset table.add("charVar", javacast("char", 'c'))> 
<cfset table.add("booleanVar", javacast("boolean", "yes"))> 
<cfset table.add("StringVar", "Hello World")> 
<cfset table.add("decimalVar", javacast("bigdecimal", 123234234.505))> 
 
<!--- call HashTable.add(Object, Object) for unsigned primitive types. ---> 
<cfset boxedByte = createObject(".NET", "System.BoxedByte").init(10)> 
<cfset table.add("byteVar", boxedByte)> 
 
<cfset boxedUShort = createObject(".NET", "System.BoxedUShort").init(100)> 
<cfset table.add("ushortVar", boxedUShort)> 
 
<cfset boxedUInt = createObject(".NET", "System.BoxedUInt").init(123)> 
<cfset table.add("uintVar", boxedUInt)> 
 
<cfset boxedULong = createObject(".NET", "System.BoxedULong").init(123123)> 
<cfset table.add("ulongVar", boxedULong)> 
 
<cfdump var="#DotNetToCFType(table)#">

Any other .NET objects can be passed as it is.

ColdFusion cannot determine the correct data type conversion if a method has multiple signatures with the same number of parameters that differ only in the parameter data types. In this case, use the JavaCast method to convert the ColdFusion data to the Java type that corresponds to the .NET type.

For example, if a .NET class has methods myFunc(ulong) and myFunc(int), use the JavaCast method to convert your ColdFusion variable to the Java float or int data type, as the following line shows:

myFunc(JavaCast(int, MyVar));

Similarly, if a .NET class has methods myFunc(int) and myFunc(String), use the JavaCast method to convert your ColdFusion variable to the Java int or String data type, as shown in the following line:

myFunc(JavaCast(String, "123");

In some cases, the JavaCast function cannot eliminate ambiguity because a single Java type corresponds to multiple .NET types. In these cases, ColdFusion creates a proxy with only one method, which uses the .NET data type that corresponds directly to a Java type.

For example, if the .NET class has methods myFunc(ulong) and myFunc(float), the generated proxy has only one method. This method calls myFunc(float), because the Java float type used to handle ColdFusion floating-point numbers corresponds directly to the .NET float type. In this case, you can never call the .NET myFunc(ulong) method.

.NET Hashtables are case sensitive, but most methods of ColdFusion structure access are not case sensitive. Only associative array notation of the form structName["keyName"] is case sensitive. When .NET Hashtables are converted to CF structure, the entire data set is converted, even if the element keys differ only in case. Therefore, to get the values of the keys that differ only in case, use associative array notation.

The following example shows this issue. It creates a Hashtable object with three entries whose key values vary only in case. In the example, output using dot-delimited structure notation always returns the same value, corresponding to the all-uppercase key, but associative array notation returns the correct result.

<!--- Create a Hashtable and convert it to a ColdFusion structure. ---> 
<cfset table = createObject(".NET", "System.Collections.Hashtable")> 
<cfset table.add("Key", "Value1")> 
<cfset table.add("KEY", "Value2")> 
<cfset table.add("key", "Value3")> 
<cfset cftable = DotNetToCFType(table)> 
 
<cfdump var="#cftable#"> 
 
<h3>Using dot notation</h3> 
Key : <cfoutput>#cftable.Key#</cfoutput><br> 
KEY : <cfoutput>#cftable.KEY#</cfoutput><br> 
key : <cfoutput>#cftable.key#</cfoutput><br> 
<p> 
 
<h3>Using associative array notation</h3> 
Key : <cfoutput>#cftable["Key"]#</cfoutput><br> 
KEY : <cfoutput>#cftable["KEY"]#</cfoutput><br> 
key : <cfoutput>#cftable["key"]#</cfoutput><br>

ColdFusion converts System.Collections.ArrayList objects to ColdFusion arrays, and you can perform all standard ColdFusion array operations on them. The following example shows this usage:

.Net Code:

public ArrayList getList(){ 
    ArrayList myAL = new ArrayList(); 
    myAL.Add("Hello"); 
    myAL.Add(1); 
    myAL.add(true); 
    Return AL; 
}

ColdFusion Code:

<cfset cflist = netObject.getList()> 
<cfloop array="#cflist#" index="item"> 
    <cfoutput>#item#</cfoutput><br> 
</cfloop> 
     
<cfif cflist[3]> 
        <cfoutput>Third element in the list is true</cfoutput> 
</cfif>

ColdFusion converts System.Data.DataTable objects to ColdFusion query objects, and you can perform all standard ColdFusion query operations on them. The following example shows this usage:

.Net code:

public DataTable datasetMethod() 
{ 
    //conn string 
    string connectionString = "..."; 
     
    //connection 
    using (SqlConnection connection = new SqlConnection(connectionString)) 
    { 
        SqlCommand cmd = new SqlCommand(@"SELECT * FROM [tblEmployees]", connection); 
        connection.Open(); 
        SqlDataReader reader = cmd.ExecuteReader(); 
        DataTable dt = new DataTable(); 
        dt.Load(reader); 
        return dt; 
} 
}

ColdFusion code:

<cfset query1 = netObject.datasetMethod()> 
<cfoutput query="query1"> 
    Query1.CurrentRow = #query1.CurrentRow#<br> 
</cfoutput>

When a .NET method returns an ArrayList, Hashtable, or DataTable, ColdFusion automatically converts it to a ColdFusion array, structure, or query, respectively. However ColdFusion does not automatically convert from ColdFusion data types to these .NET types. (ColdFusion does automatically convert ColdFusion arrays to .Net array types.) Therefore, you cannot use ColdFusion variables directly as input parameters to .NET object instance methods that require .NET System.Collection.ArrayList, System.Collection.Hashtable, or System.Data.DataTable types. Instead create instances of these .NET types and populate them with the required data before you pass them to the .NET method. For an example of creating and populating a System.Collection.Hashtable object, see the example at the end of the “Converting data to System.Object type” section.

You can disable automatic conversion of .NET System.Collections.Hashtable, System.Collections.ArrayList or System.Data.DataTable objects to the corresponding ColdFusion structure, array, or query objects. You could want to disable the conversion under the following circumstances:

• If a collection or DataTable returned by a .NET method is large and you only want a small subset of the data. If auto conversion is enabled, ColdFusion creates a data structure with all the object’s fields. Creating the structure could take significant time and resources, because ColdFusion must invoke .NET methods internally to get each of the fields. You can disable the automatic conversion and retrieve the fields or data from .NET objects like any other objects.

• If you invoke a .NET method that returns a complex variable, and then pass the variable to another .NET method as argument. If automatic conversion is enabled, you cannot pass the Hashtable object from the first method directly to the second method.

To disable automatic conversion, set the JVM coldfusion.dotnet.disableautoconversion system property to true. For example, in a ColdFusion stand-alone server, or if you use JRun as your J2EE server, include the following setting in the JVM.config file:

-Dcoldfusion.dotnet.disableautoconversion=true

Use the DotNetToCFType function to convert a System.Collections.Hashtable, System.Collections.ArrayList or System.Data.DataTable object to a ColdFusion structure, array, or query respectively when either of the following circumstances are true:

• You have set the coldfusion.dotnet.disableautoconversion system property to true.

• Automatic conversion is enabled, you created the complex .NET object by using the createObject function or cfobject tag, and you want to convert this object into the corresponding ColdFusion representation.

For an example of using the function, see DotNetToCFType in the CFML Reference.

.NET fields and return values with class types are available in ColdFusion as .NET objects. You can use the object’s methods to access object data and make it available to ColdFusion using supported data types.

The following example gets information about a system’s drives. It calls the System.IO.DriveInfo.GetDrives() method to get an array of System.IO.DriveInfo objects, one per drive. It then calls the object methods to get specific information about the drives, and displays the information. The example uses a cfdump tag to simplify the code.

<!--- Create a query for the drive information results. --->  
<cfset result=QueryNew("name,type,isready,format,label,totalsize,freespace" 
                    ,"varchar,varchar,bit,varchar,varchar,double,double")> 
<!--- Create a .NET System.IO.DriveInfo object. ---> 
<cfobject type=".NET" name="sidiClass" class="System.IO.DriveInfo"> 
<!--- Get the drives. ---> 
<cfset drives=sidiClass.GetDrives()> 
<!--- Loop through drives. ---> 
<cfloop from="1" to="#ArrayLen(drives)#" index="i"> 
    <!--- Add a row to the query.---> 
    <cfset QueryAddRow(result)> 
    <!--- Get the drive name, type, and ready flag. ---> 
    <cfset QuerySetCell(result, "name", drives[i].Get_Name())> 
    <cfset QuerySetCell(result, "type", 
                drives[i].Get_DriveType().ToString())> 
    <cfset QuerySetCell(result, "isready", drives[i].Get_IsReady())> 
    <!--- Get extra details ONLY if the drive is ready. ---> 
    <cfif drives[i].Get_IsReady()> 
        <cfset QuerySetCell(result, "format", drives[i].Get_DriveFormat())> 
        <cfset QuerySetCell(result, "label", drives[i].Get_VolumeLabel())> 
        <cfset QuerySetCell(result, "totalsize", drives[i].Get_TotalSize())> 
        <cfset QuerySetCell(result, "freespace", 
                    drives[i].Get_AvailableFreeSpace())> 
    </cfif> 
</cfloop> 
<cfdump var="#result#">