Convert SQL Type to .NET Type

SqlUtilities.GetDotnetType.cs

public static class SqlUtilities
{
	readonly static SqlDataTypeOption[] unsupportedTypes = new[]
	{
		SqlDataTypeOption.Sql_Variant,
		SqlDataTypeOption.Timestamp,
		SqlDataTypeOption.Rowversion,
	};
	
	public static string GetDotnetType(this SqlDataTypeOption sqlDataType, bool isNullable = false)
	{
		if (IsUnsupportedType())
		{
		    return string.Empty;
		}

		var dotnetType = typeof(string);
		switch (sqlDataType)
		{
		    case SqlDataTypeOption.BigInt: dotnetType = typeof(long); break;
		    case SqlDataTypeOption.Binary:
		    case SqlDataTypeOption.Image:
		    case SqlDataTypeOption.VarBinary: dotnetType = typeof(byte[]); break;
		    case SqlDataTypeOption.Bit: dotnetType = typeof(bool); break;
		    case SqlDataTypeOption.Char: dotnetType = typeof(char); break;
		    case SqlDataTypeOption.Time: dotnetType = typeof(TimeOnly); break;
		    case SqlDataTypeOption.Date: dotnetType = typeof(DateOnly); break;
		    case SqlDataTypeOption.DateTime:
		    case SqlDataTypeOption.SmallDateTime: dotnetType = typeof(DateTime); break;
		    case SqlDataTypeOption.DateTime2:
		    case SqlDataTypeOption.DateTimeOffset: dotnetType = typeof(DateTimeOffset); break;
		    case SqlDataTypeOption.Decimal:
		    case SqlDataTypeOption.Money:
		    case SqlDataTypeOption.Numeric: dotnetType = typeof(decimal); break;
		    case SqlDataTypeOption.Float: dotnetType = typeof(double); break;
		    case SqlDataTypeOption.Int: dotnetType = typeof(int); break;
		    case SqlDataTypeOption.NChar:
		    case SqlDataTypeOption.NVarChar:
		    case SqlDataTypeOption.Text:
		    case SqlDataTypeOption.VarChar: dotnetType = typeof(string); break;
		    case SqlDataTypeOption.Real: dotnetType = typeof(float); break;
		    case SqlDataTypeOption.SmallInt: dotnetType = typeof(short); break;
		    case SqlDataTypeOption.TinyInt: dotnetType = typeof(byte); break;
		    case SqlDataTypeOption.UniqueIdentifier: dotnetType = typeof(Guid); break;
		}

		return dotnetType.Name + (isNullable ? "?" : string.Empty);

		bool IsUnsupportedType()
		{
			return unsupportedTypes.Contains(sqlDataType);
		}
	}

	public static string GetDotnetType(this string sqlDataType, bool isNullable = false)
	{
		RemoveAnyPercision();

		if (!Enum.TryParse(sqlDataType, true, out SqlDataTypeOption dataTypeOption))
		{
			return string.Empty;
		}

		return dataTypeOption.GetDotnetType(isNullable);

		void RemoveAnyPercision()
		{
			int index = sqlDataType.IndexOf("(");
			if (index != -1)
			{
				sqlDataType = sqlDataType.Substring(0, index).Trim();
			}
		}
	}
}

On the left is the original code and IsUnsupportedType creates a newarr each time its called.
On the right, the code uses the defined array unsupportedtypes.

On the right the static ctor (cctor) creates the unsupported type once and reuses