ASP .NET MVC — Set precision for Decimal for Entity Framework Code First

We found that the table only contained two decimal places and we want to save more place in the SQL server.

Introduction

For SQL Server, we have to decide the precision for the decimal type. For example, decimal(10, 3) means 7 integer place and 3 decimal place.

However, the precision for the C# code mapping to SQL Server is fixed to decimal(18, 2) when we use Entity Framework Code First.

The solution is quite simple.

Solution

There are 2 methods to solve this problem.

1. Set precision by using modelBuilder

The first method is to set precision by using modelBuilder.

2. Write customized convention

The disadvantage of the first method to solve this problem is that you have to remember to modify OnModelCreating(). An alternative way is to create a customized convention.

• ConventionPrimitivePropertyConfiguration provides different methods to configure the primitive properties of an entity type or complex type.
• In this case, we use ConventionPrimitivePropertyConfiguration.HasPrecision.
• We can set the precision of decimal by using following steps.

1. Create a convention which inherits from the PrimitivePropertyAttributeConfigurationConvention. It can help us to configure the property from ConventionPrimitivePropertyConfiguration.

2. Create a customized attribute which inherits attribute. It’s the type to enter the PrimitivePropertyAttributeConfigurationConvention.

3. Tell Entity Framework to use our convention. Add it to conventions collection in OnModelCreating.

4. Decorate our model by using this convention.

[DecimalPrecision(10, 3)]
public decimal Longitude { get; set; }

References

• 解决 Entity Framework 6.0 decimal 类型精度问题
• Entity Framework Code First建立Decimal，並設定大小
• Set decimal(16, 3) for a column in Code First Approach in EF4.3

Summary

Thanks for your patient. I am Sean. I work as a software engineer.

This article is my note. Please feel free to give me advice if any mistakes. I am looking forward to your feedback.

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