DllImportAttribute.BestFitMapping Field

Reference

Definition

Namespace:: System.Runtime.InteropServices

Assemblies:: mscorlib.dll, System.Runtime.InteropServices.dll

Assemblies:: netstandard.dll, System.Runtime.InteropServices.dll

Assembly:: System.Runtime.InteropServices.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: DllImportAttribute.cs

Source:: DllImportAttribute.cs

Source:: DllImportAttribute.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Enables or disables best-fit mapping behavior when converting Unicode characters to ANSI characters.

public: bool BestFitMapping;

public bool BestFitMapping;

val mutable BestFitMapping : bool

Public BestFitMapping As Boolean

Field Value

Boolean

Examples

In some cases, Visual Basic developers use the DllImportAttribute, instead of the Declare statement, to define a DLL function in managed code. Setting the BestFitMapping field is one of those cases. The following example shows how to apply the strictest character mapping security to a platform invoke method definitions by specifying the ANSI character set, disabling best fit mapping behavior, and throwing an exception on unmapped Unicode characters.

[DllImport("My.dll", CharSet = CharSet::Ansi,
    BestFitMapping = false,
    ThrowOnUnmappableChar = true)]
int SomeFuncion2(int parm);

[DllImport("My.dll", CharSet = CharSet.Ansi,
    BestFitMapping = false,
    ThrowOnUnmappableChar = true)]
internal static extern int SomeFuncion2(int parm);

<DllImport("My.dll", CharSet:=CharSet.Ansi,
    BestFitMapping:=False,
    ThrowOnUnmappableChar:=True)>
Friend Shared Function SomeFuncion2(parm As Integer) As Integer
End Function

Remarks

If true, best-fit mapping behavior is enabled; otherwise, best-fit mapping is disabled. The BestFitMapping field is true by default. Settings for this field override the any level settings for the System.Runtime.InteropServices.BestFitMappingAttribute attribute.

Varning

Certain Unicode characters are converted to dangerous characters, such as the backslash '\' character, which can inadvertently change a path. By setting the ThrowOnUnmappableChar field to true, you can signal the presence of an unmappable character to the caller by throwing an exception.

Varning

You cannot change the default values provided by the BestFitMapping and ThrowOnUnmappableChar fields when passing a managed array whose elements are ANSI Chars or LPSTRs to an unmanaged safe array. Best-fit mapping is always enabled and no exception is thrown. Be aware that this combination can compromise your security model.

Applies to

Produkt	Versioner
.NET	Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP	10.0

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