Mapping CLR Parameter Data

The following table lists Microsoft SQL Server data types, their equivalents in the common language runtime (CLR) for SQL Server in the System.Data.SqlTypes namespace, and their native CLR equivalents in the Microsoft .NET Framework.

SQL Server data type Type (in System.Data.SqlTypes or Microsoft.SqlServer.Types) CLR data type (.NET Framework)
bigint SqlInt64 Int64, Nullable<Int64>
binary SqlBytes, SqlBinary Byte[]
bit SqlBoolean Boolean, Nullable<Boolean>
char None None
cursor None None
date SqlDateTime DateTime, Nullable<DateTime>
datetime SqlDateTime DateTime, Nullable<DateTime>
datetime2 None DateTime, Nullable<DateTime>
DATETIMEOFFSET None DateTimeOffset, Nullable<DateTimeOffset>
decimal SqlDecimal Decimal, Nullable<Decimal>
float SqlDouble Double, Nullable<Double>
geography SqlGeography

SqlGeography is defined in Microsoft.SqlServer.Types.dll, which is installed with SQL Server and can be downloaded from the SQL Server 2016 feature pack.
None
geometry SqlGeometry

SqlGeometry is defined in Microsoft.SqlServer.Types.dll, which is installed with SQL Server and can be downloaded from the SQL Server 2016 feature pack.
None
hierarchyid SqlHierarchyId

SqlHierarchyId is defined in Microsoft.SqlServer.Types.dll, which is installed with SQL Server and can be downloaded from the SQL Server 2016 feature pack.
None
image None None
int SqlInt32 Int32, Nullable<Int32>
money SqlMoney Decimal, Nullable<Decimal>
nchar SqlChars, SqlString String, Char[]
ntext None None
numeric SqlDecimal Decimal, Nullable<Decimal>
nvarchar SqlChars, SqlString

SQLChars is a better match for data transfer and access, and SQLString is a better match for performing String operations.
String, Char[]
nvarchar(1), nchar(1) SqlChars, SqlString Char, String, Char[], Nullable<char>
real SqlSingle (the range of SqlSingle, however, is larger than real) Single, Nullable<Single>
rowversion None Byte[]
smallint SqlInt16 Int16, Nullable<Int16>
smallmoney SqlMoney Decimal, Nullable<Decimal>
sql_variant None Object
table None None
text None None
time None TimeSpan, Nullable<TimeSpan>
timestamp None None
tinyint SqlByte Byte, Nullable<Byte>
uniqueidentifier SqlGuid Guid, Nullable<Guid>
User-defined type(UDT) None The same class that is bound to the user-defined type in the same assembly or a dependent assembly.
varbinary SqlBytes, SqlBinary Byte[]
varbinary(1), binary(1) SqlBytes, SqlBinary byte, Byte[], Nullable<byte>
varchar None None
xml SqlXml None

Automatic Data Type Conversion with Out Parameters

A CLR method can return information to the calling code or program by marking an input parameter with the out modifier (Microsoft Visual C#) or <Out()> ByRef (Microsoft Visual Basic) If the input parameter is a CLR data type in the System.Data.SqlTypes namespace, and the calling program specifies its equivalent SQL Server data type as the input parameter, a type conversion occurs automatically when the CLR method returns the data type.

For example, the following CLR stored procedure has an input parameter of SqlInt32 CLR data type that is marked with out (C#) or <Out()> ByRef (Visual Basic):

[Microsoft.SqlServer.Server.SqlProcedure]  
public static void PriceSum(out SqlInt32 value)  
{ … }  
\<Microsoft.SqlServer.Server.SqlProcedure> _  
Public Shared Sub PriceSum( \<Out()> ByRef value As SqlInt32)  
…  
End Sub  

After the assembly is built and created in the database, the stored procedure is created in SQL Server with the following Transact-SQL, which specifies a SQL Server data type of int as an OUTPUT parameter:

CREATE PROCEDURE PriceSum (@sum int OUTPUT)  
AS EXTERNAL NAME TestStoredProc.StoredProcedures.PriceSum  

When the CLR stored procedure is called, the SqlInt32 data type is automatically converted to an int data type, and returned to the calling program.

Not all CLR data types can be automatically converted to their equivalent SQL Server data types through an out parameter, however. The following table lists these exceptions.

CLR data type (SQL Server) SQL Server data type
Decimal smallmoney
SqlMoney smallmoney
Decimal money
DateTime smalldatetime
SQLDateTime smalldatetime

Change History

Updated content
Added SqlGeography, SqlGeometry, and SqlHierarchyId types to the mapping table.

See Also

SQL Server Data Types in the .NET Framework