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For the following SQL Server datatypes, what would be the corresponding datatype in C#?

Exact Numerics

bigint
numeric
bit
smallint
decimal
smallmoney
int
tinyint
money

Approximate Numerics

float
real

Date and Time

date
datetimeoffset
datetime2
smalldatetime
datetime
time

Character Strings

char
varchar
text

Unicode Character Strings

nchar
nvarchar
ntext

Binary Strings

binary
varbinary
image

Other Data Types

cursor
timestamp
hierarchyid
uniqueidentifier
sql_variant
xml
table

(source: MSDN)

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5 Answers 5

Reset to default
1345

This is for SQL Server 2005. There are updated versions of the table for SQL Server 2008, SQL Server 2008 R2, SQL Server 2012 and SQL Server 2014.

SQL Server Data Types and Their .NET Framework Equivalents

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 CLR data type (SQL Server) CLR data type (.NET Framework)
varbinary SqlBytes, SqlBinary Byte[]
binary SqlBytes, SqlBinary Byte[]
varbinary(1), binary(1) SqlBytes, SqlBinary byte, Byte[]
image None None
varchar None None
char None None
nvarchar(1), nchar(1) SqlChars, SqlString Char, String, Char[]
nvarchar SqlChars, SqlString String, Char[]
nchar SqlChars, SqlString String, Char[]
text None None
ntext None None
uniqueidentifier SqlGuid Guid
rowversion None Byte[]
bit SqlBoolean Boolean
tinyint SqlByte Byte
smallint SqlInt16 Int16
int SqlInt32 Int32
bigint SqlInt64 Int64
smallmoney SqlMoney Decimal
money SqlMoney Decimal
numeric SqlDecimal Decimal
decimal SqlDecimal Decimal
real SqlSingle Single
float SqlDouble Double
smalldatetime SqlDateTime DateTime
datetime SqlDateTime DateTime
sql_variant None Object
User-defined type(UDT) None user-defined type
table None None
cursor None None
timestamp None None
xml SqlXml None
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  • 1
    Which CLR data type (SQL Server) should be used for short in .Net framework ?
    – Yogesh Patel
    Commented Apr 13, 2018 at 8:28
  • 9
    @yogeshpatel, short (learn.microsoft.com/en-us/dotnet/csharp/language-reference/…) is equal to System.Int16 in this listing. So that would be smallint in SQL Server.
    – Örjan Jämte
    Commented Apr 16, 2018 at 8:44
  • 1
    Important note: SQL data type "float" defaults to "float(54)" which converts to C# "double". HOWEVER, SQL datatype "float(24)" converts to C# "float" only. So if you don't need many digits of precision and want to improve performance/memory, use float(24) in SQL and types "float" in C#.
    – Jason
    Commented Feb 13, 2021 at 0:37
102

SQL Server and .Net Data Type mapping

SQL Server and .Net Data Type mapping

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In case anybody is looking for methods to convert from/to C# and SQL Server formats, here goes a simple implementation:

private readonly string[] SqlServerTypes = { "bigint", "binary", "bit",  "char", "date",     "datetime", "datetime2", "datetimeoffset", "decimal", "filestream", "float",  "geography",                              "geometry",                              "hierarchyid",                              "image",  "int", "money",   "nchar",  "ntext",  "numeric", "nvarchar", "real",   "rowversion", "smalldatetime", "smallint", "smallmoney", "sql_variant", "text",   "time",     "timestamp", "tinyint", "uniqueidentifier", "varbinary", "varchar", "xml" };
private readonly string[] CSharpTypes    = { "long",   "byte[]", "bool", "char", "DateTime", "DateTime", "DateTime",  "DateTimeOffset", "decimal", "byte[]",     "double", "Microsoft.SqlServer.Types.SqlGeography", "Microsoft.SqlServer.Types.SqlGeometry", "Microsoft.SqlServer.Types.SqlHierarchyId", "byte[]", "int", "decimal", "string", "string", "decimal", "string",   "Single", "byte[]",     "DateTime",      "short",    "decimal",    "object",      "string", "TimeSpan", "byte[]",    "byte",    "Guid",             "byte[]",    "string",  "string" };

public string ConvertSqlServerFormatToCSharp(string typeName)
{
    var index = Array.IndexOf(SqlServerTypes, typeName);

    return index > -1
        ? CSharpTypes[index]
        : "object";
}

public string ConvertCSharpFormatToSqlServer(string typeName)
{
    var index = Array.IndexOf(CSharpTypes, typeName);

    return index > -1
        ? SqlServerTypes[index]
        : null;
}

Edit: fixed typo

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  • 2
    Your method ConvertCSharpFormatToSqlServer will only always return the first instance found as CSharp Types are not unique, i.e. "byte[]" will always return "binary" even though it's mapped to 5 other Sql Server Types.
    – David
    Commented Sep 26, 2020 at 8:17
  • 1
    @David although what you said is not technicaly wrong, it makes sense when you are using the ConvertSqlServerFormatToCSharp method. This is just an example, you can always modify it for your own needs.
    – AndreFeijo
    Commented Sep 28, 2020 at 9:36
8

SQL Server and the .NET Framework are based on different type systems. For example, the .NET Framework Decimal structure has a maximum scale of 28, whereas the SQL Server decimal and numeric data types have a maximum scale of 38. Click Here's a link! for detail

https://msdn.microsoft.com/en-us/library/cc716729(v=vs.110).aspx

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8 
public static string FromSqlType(string sqlTypeString)
{
    if (! Enum.TryParse(sqlTypeString, out Enums.SQLType typeCode))
    {
        throw new Exception("sql type not found");
    }
    switch (typeCode)
    {
        case Enums.SQLType.varbinary:
        case Enums.SQLType.binary:
        case Enums.SQLType.filestream:
        case Enums.SQLType.image:
        case Enums.SQLType.rowversion:
        case Enums.SQLType.timestamp://?
            return "byte[]";
        case Enums.SQLType.tinyint:
            return "byte";
        case Enums.SQLType.varchar:
        case Enums.SQLType.nvarchar:
        case Enums.SQLType.nchar:
        case Enums.SQLType.text:
        case Enums.SQLType.ntext:
        case Enums.SQLType.xml:
            return "string";
        case Enums.SQLType.@char:
            return "char";
        case Enums.SQLType.bigint:
            return "long";
        case Enums.SQLType.bit:
            return "bool";
        case Enums.SQLType.smalldatetime:
        case Enums.SQLType.datetime:
        case Enums.SQLType.date:
        case Enums.SQLType.datetime2:
            return "DateTime";
        case Enums.SQLType.datetimeoffset:
            return "DateTimeOffset";
        case Enums.SQLType.@decimal:
        case Enums.SQLType.money:
        case Enums.SQLType.numeric:
        case Enums.SQLType.smallmoney:
            return "decimal";
        case Enums.SQLType.@float:
            return "double";
        case Enums.SQLType.@int:
            return "int";
        case Enums.SQLType.real:
            return "Single";
        case Enums.SQLType.smallint:
            return "short";
        case Enums.SQLType.uniqueidentifier:
            return "Guid";
        case Enums.SQLType.sql_variant:
            return "object";
        case Enums.SQLType.time:
            return "TimeSpan";
        default:
            throw new Exception("none equal type");
    }
}

public enum SQLType
{
    varbinary,//(1)
    binary,//(1)
    image,
    varchar,
    @char,
    nvarchar,//(1)
    nchar,//(1)
    text,
    ntext,
    uniqueidentifier,
    rowversion,
    bit,
    tinyint,
    smallint,
    @int,
    bigint,
    smallmoney,
    money,
    numeric,
    @decimal,
    real,
    @float,
    smalldatetime,
    datetime,
    sql_variant,
    table,
    cursor,
    timestamp,
    xml,
    date,
    datetime2,
    datetimeoffset,
    filestream,
    time,
}
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