58 lines
1.5 KiB
Markdown
58 lines
1.5 KiB
Markdown
# Relaxed rules for auto-properties in structs
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Before C# 6.0 you could not write code like this:
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```csharp
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struct S
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{
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int X { get; set; }
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int Y { get; set; }
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public S(int x, int y)
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{
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this.X = x;
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this.Y = y;
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}
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}
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```
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```none
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error CS0188: The 'this' object cannot be used before all of its fields are assigned to
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error CS0843: Backing field for automatically implemented property 'S.X' must be fully assigned before control is returned to the caller. Consider calling the default constructor from a constructor initializer.
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error CS0843: Backing field for automatically implemented property 'S.Y' must be fully assigned before control is returned to the caller. Consider calling the default constructor from a constructor initializer.
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```
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A workaround was to invoke the default constructor:
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```csharp
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struct S
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{
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int X { get; set; }
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int Y { get; set; }
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public S(int x, int y) : this()
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{
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this.X = x;
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this.Y = y;
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}
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}
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```
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or to initialize this to the default value:
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```csharp
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struct S
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{
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int X { get; set; }
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int Y { get; set; }
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public S(int x, int y)
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{
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this = default(S);
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this.X = x;
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this.Y = y;
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}
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}
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```
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Unfortunately, both methods effectively disabled definite assignment analysis for instance fields for the given constructor.
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C# 6.0 relaxes these rules by tracking assignments to instance auto-properties as if they were assignments to their backing fields, so the code in the beginning of this section is now valid.
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