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11/18/2011

Type.GetType Method (String, Boolean, Boolean)

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Gets the Type with the specified name, specifying whether to perform a case-sensitive search and whether to throw an exception if the type is not found.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
Public Shared Function GetType ( _
    typeName As String, _
    throwOnError As Boolean, _
    ignoreCase As Boolean _
) As Type

public static Type GetType(
    string typeName,
    bool throwOnError,
    bool ignoreCase
)

Parameters

typeName
Type: System.String
The assembly-qualified name of the type to get. See AssemblyQualifiedName. If the type is in the currently executing assembly or in Mscorlib.dll, it is sufficient to supply the type name qualified by its namespace.

throwOnError
Type: System.Boolean
true to throw an exception if the type cannot be found; false to return nulla null reference (Nothing in Visual Basic). Specifying false also suppresses some other exception conditions, but not all of them. See the Exceptions section.

ignoreCase
Type: System.Boolean
true to perform a case-insensitive search for typeName, false to perform a case-sensitive search for typeName.

Return Value

Type: System.Type
The type with the specified name. If the type is not found, the throwOnError parameter specifies whether nulla null reference (Nothing in Visual Basic) is returned or an exception is thrown. In some cases, an exception is thrown regardless of the value of throwOnError. See the Exceptions section.

Exceptions

Exception	Condition
ArgumentNullException	typeName is nulla null reference (Nothing in Visual Basic).
TargetInvocationException	A class initializer is invoked and throws an exception.
TypeLoadException	throwOnError is true and the type is not found. -or- throwOnError is true and typeName contains invalid characters, such as an embedded tab. -or- throwOnError is true and typeName is an empty string. -or- throwOnError is true and typeName represents an array type with an invalid size. -or- typeName represents an array of TypedReference.
ArgumentException	throwOnError is true and typeName contains invalid syntax. For example, "MyType[,*,]". -or- typeName represents a generic type that has a pointer type, a ByRef type, or Void as one of its type arguments. -or- typeName represents a generic type that has an incorrect number of type arguments. -or- typeName represents a generic type, and one of its type arguments does not satisfy the constraints for the corresponding type parameter.
FileNotFoundException	throwOnError is true and the assembly or one of its dependencies was not found.
FileLoadException	The assembly or one of its dependencies was found, but could not be loaded.
BadImageFormatException	The assembly or one of its dependencies is not valid. -or- The assembly was compiled with a later version of the .NET Framework.

Remarks

You can use the GetType method to obtain a Type object for a type in another assembly, if the you know its namespace-qualified name. GetType causes loading of the assembly specified in typeName. You can also load an assembly using the Load method, and then use the GetType or GetTypes methods of the Assembly class to get Type objects. If a type is in an assembly known to your program at compile time, it is more efficient to use typeof in C#, GetType in Visual Basic, or typeid in C++.

GetType only works on assemblies loaded from disk. If you call GetType to look up a type defined in a dynamic assembly defined using the System.Reflection.Emit services, you might get inconsistent behavior. The behavior depends on whether the dynamic assembly is persistent, that is, created using the RunAndSave or Save access modes of the System.Reflection.Emit.AssemblyBuilderAccess enumeration. If the dynamic assembly is persistent and has been written to disk before GetType is called, the loader finds the saved assembly on disk, loads that assembly, and retrieves the type from that assembly. If the assembly has not been saved to disk when GetType is called, the method returns nulla null reference (Nothing in Visual Basic). GetType does not understand transient dynamic assemblies; therefore, calling GetType to retrieve a type in a transient dynamic assembly returns nulla null reference (Nothing in Visual Basic).

To use GetType on a dynamic module, subscribe to the AppDomain.AssemblyResolve event and call GetType before saving. Otherwise, you will get two copies of the assembly in memory.

The throwOnError parameter specifies what happens when the type is not found, and also suppresses certain other exception conditions, as described in the Exceptions section. Some exceptions are thrown regardless of the value of throwOnError. For example, if the type is found but cannot be loaded, a TypeLoadException is thrown even if throwOnError is false.

The following table shows what members of a base class are returned by the Get methods when reflecting on a type.

Member Type	Static	Non-Static
Constructor	No	No
Field	No	Yes. A field is always hide-by-name-and-signature.
Event	Not applicable	The common type system rule is that the inheritance is the same as that of the methods that implement the property. Reflection treats properties as hide-by-name-and-signature. See note 2 below.
Method	No	Yes. A method (both virtual and non-virtual) can be hide-by-name or hide-by-name-and-signature.
Nested Type	No	No
Property	Not applicable	The common type system rule is that the inheritance is the same as that of the methods that implement the property. Reflection treats properties as hide-by-name-and-signature. See note 2 below.

Notes:

Hide-by-name-and-signature considers all of the parts of the signature, including custom modifiers, return types, parameter types, sentinels, and unmanaged calling conventions. This is a binary comparison.
For reflection, properties and events are hide-by-name-and-signature. If you have a property with both a get and a set accessor in the base class, but the derived class has only a get accessor, the derived class property hides the base class property, and you will not be able to access the setter on the base class.
Custom attributes are not part of the common type system.

Arrays or COM types are not searched for unless they have already been loaded into the table of available classes.

typeName can be the type name qualified by its namespace or an assembly-qualified name that includes an assembly name specification. See AssemblyQualifiedName.

If typeName includes the namespace but not the assembly name, this method searches only the calling object's assembly and Mscorlib.dll, in that order. If typeName is fully qualified with the partial or complete assembly name, this method searches in the specified assembly. If the assembly has a strong name, a complete assembly name is required.

The AssemblyQualifiedName property returns a fully qualified type name including nested types, the assembly name, and type arguments. All compilers that support the common language runtime will emit the simple name of a nested class, and reflection constructs a mangled name when queried, in accordance with the following conventions.

Delimiter	Meaning
Backslash (\)	Escape character.
Backtick (`)	Precedes one or more digits representing the number of type parameters, located at the end of the name of a generic type.
Brackets ([])	Enclose a generic type argument list, for a constructed generic type; within a type argument list, enclose an assembly-qualified type.
Comma (,)	Precedes the Assembly name.
Period (.)	Denotes namespace identifiers.
Plus sign (+)	Precedes a nested class.

For example, the fully qualified name for a class might look like this:

TopNamespace.SubNameSpace.ContainingClass+NestedClass,MyAssembly

If the namespace were TopNamespace.Sub+Namespace, then the string would have to precede the plus sign (+) with an escape character (\) to prevent it from being interpreted as a nesting separator. Reflection emits this string as follows:

TopNamespace.Sub\+Namespace.ContainingClass+NestedClass,MyAssembly

A "++" becomes "\+\+", and a "\" becomes "\\".

This qualified name can be persisted and later used to load the Type. To search for and load a Type, use GetType either with the type name only or with the assembly qualified type name. GetType with the type name only will look for the Type in the caller's assembly and then in the System assembly. GetType with the assembly qualified type name will look for the Type in any assembly.

Type names may include trailing characters that denote additional information about the type, such as whether the type is a reference type, a pointer type or an array type. To retrieve the type name without these trailing characters, use t.GetElementType().ToString(), where t is the type.

Spaces are relevant in all type name components except the assembly name. In the assembly name, spaces before the ',' separator are relevant, but spaces after the ',' separator are ignored.

The name of a generic type ends with a backtick (`) followed by digits representing the number of generic type arguments. The purpose of this name mangling is to allow compilers to support generic types with the same name but with different numbers of type parameters, occurring in the same scope. For example, reflection returns the mangled names Tuple`1 and Tuple`2 from the generic methods Tuple(Of T) and Tuple(Of T0, T1) in Visual Basic, or Tuple<T> and Tuple<T0, T1> in Visual C#.

For generic types, the type argument list is enclosed in brackets, and the type arguments are separated by commas. For example, a generic Dictionary<TKey, TValue> has two type parameters. A Dictionary<TKey, TValue> of MyType with keys of type String might be represented as follows:

System.Collections.Generic.Dictionary`2[System.String,MyType]

To specify an assembly-qualified type within a type argument list, enclose the assembly-qualified type within brackets. Otherwise, the commas that separate the parts of the assembly-qualified name are interpreted as delimiting additional type arguments. For example, a Dictionary<TKey, TValue> of MyType from MyAssembly.dll, with keys of type String, might be specified as follows:

Type.GetType("System.Collections.Generic.Dictionary`2[System.String,[MyType,MyAssembly]]")

Note:
An assembly-qualified type can be enclosed in brackets only when it appears within a type parameter list. The rules for searching assemblies for qualified and unqualified types in type parameter lists are the same as the rules for qualified and unqualified nongeneric types.

Nullable types are a special case of generic types. For example, a nullable Int32 is represented by the string "System.Nullable`1[System.Int32]".

Note:
In C#, C++, and Visual Basic you can also get nullable types using type operators. For example, the nullable Boolean type is returned by typeof(Nullable<bool>) in C#, by Nullable<Boolean>::typeid in C++, and by GetType(Nullable(Of Boolean)) in Visual Basic.

The following table shows the syntax you use with GetType for various types.

To Get	Use
A nullable Int32	Type.GetType("System.Nullable`1[System.Int32]")
An unmanaged pointer to MyType	Type.GetType("MyType*")
An unmanaged pointer to a pointer to MyType	Type.GetType("MyType**")
A managed pointer or reference to MyType	Type.GetType("MyType&"). Note that unlike pointers, references are limited to one level.
A parent class and a nested class	Type.GetType("MyParentClass+MyNestedClass")
A one-dimensional array with a lower bound of 0	Type.GetType("MyArray[]")
A one-dimensional array with an unknown lower bound	Type.GetType("MyArray[*]")
An n-dimensional array	A comma (,) inside the brackets a total of n-1 times. For example, System.Object[,,] represents a three-dimensional Object array.
A two-dimensional array's array	Type.GetType("MyArray[][]")
A rectangular two-dimensional array with unknown lower bounds	Type.GetType("MyArray[,]")
A generic type with one type argument	Type.GetType("MyGenericType`1[MyType]")
A generic type with two type arguments	Type.GetType("MyGenericType`2[MyType,AnotherType]")
A generic type with two assembly-qualified type arguments	Type.GetType("MyGenericType`2[[MyType,MyAssembly],[AnotherType,AnotherAssembly]]")
An assembly-qualified generic type with an assembly-qualified type argument	Type.GetType("MyGenericType`1[[MyType,MyAssembly]],MyGenericTypeAssembly")
A generic type whose type argument is a generic type with two type arguments	Type.GetType("MyGenericType`1[AnotherGenericType`2[MyType,AnotherType]]")

Platform Notes

Silverlight for Windows Phone

GetType does not always throw an ArgumentException exception if you pass it an invalid parameter. Catch exceptions of type Exception to trap unexpected exceptions.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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