C# Equivalent of SQL Server DataTypes

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

SQL Server and .Net Data Type mapping

https://i.stack.imgur.com/CBhE9.png

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

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

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,
}