Converting from Type to SqlDbType

#c-sharp #stackoverflow #sql #databases

Written by Anders Marzi Tornblad

StackOverflow user Simone Salvo asked how to do a smart conversion between .Net System.Type and System.Data.SqlDbType, which is not really a trivial task.

For my answer, I wrote the following somewhat naïve code:

public class SqlHelper
    private static Dictionary<Type, SqlDbType> typeMap;

    // Create and populate the dictionary in the static constructor
    static SqlHelper()
        typeMap = new Dictionary<Type, SqlDbType>();

        typeMap[typeof(string)]         = SqlDbType.NVarChar;
        typeMap[typeof(char[])]         = SqlDbType.NVarChar;
        typeMap[typeof(byte)]           = SqlDbType.TinyInt;
        typeMap[typeof(short)]          = SqlDbType.SmallInt;
        typeMap[typeof(int)]            = SqlDbType.Int;
        typeMap[typeof(long)]           = SqlDbType.BigInt;
        typeMap[typeof(byte[])]         = SqlDbType.Image;
        typeMap[typeof(bool)]           = SqlDbType.Bit;
        typeMap[typeof(DateTime)]       = SqlDbType.DateTime2;
        typeMap[typeof(DateTimeOffset)] = SqlDbType.DateTimeOffset;
        typeMap[typeof(decimal)]        = SqlDbType.Money;
        typeMap[typeof(float)]          = SqlDbType.Real;
        typeMap[typeof(double)]         = SqlDbType.Float;
        typeMap[typeof(TimeSpan)]       = SqlDbType.Time;
        /* ... and so on ... */

    // Non-generic argument-based method
    public static SqlDbType GetDbType(Type giveType)
        if (typeMap.ContainsKey(giveType))
            return typeMap[giveType];

        throw new ArgumentException($"{giveType.FullName} is not a supported .NET class");

    // Generic version
    public static SqlDbType GetDbType<T>()
        return GetDbType(typeof(T));


The above code works fine in most cases, but comes with some problems:

The best thing would almost always be to let some ORM tool do the heavy lifting.